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Coherent and non-coherent SI units </div> </a> <ul id="toc-Coherent_and_non-coherent_SI_units-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Lexicographic_conventions" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Lexicographic_conventions"> <div class="vector-toc-text"> 2 Lexicographic conventions </div> </a> <button aria-controls="toc-Lexicographic_conventions-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> Toggle Lexicographic conventions subsection </button> <ul id="toc-Lexicographic_conventions-sublist" class="vector-toc-list"> <li id="toc-Unit_names" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Unit_names"> <div class="vector-toc-text"> 2.1 Unit names </div> </a> <ul id="toc-Unit_names-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Unit_symbols_and_the_values_of_quantities" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Unit_symbols_and_the_values_of_quantities"> <div class="vector-toc-text"> 2.2 Unit symbols and the values of quantities </div> </a> <ul id="toc-Unit_symbols_and_the_values_of_quantities-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Realisation_of_units" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Realisation_of_units"> <div class="vector-toc-text"> 3 Realisation of units </div> </a> <ul id="toc-Realisation_of_units-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Organizational_status" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Organizational_status"> <div class="vector-toc-text"> 4 Organizational status </div> </a> <button aria-controls="toc-Organizational_status-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> Toggle Organizational status subsection </button> <ul id="toc-Organizational_status-sublist" class="vector-toc-list"> <li id="toc-International_System_of_Quantities" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#International_System_of_Quantities"> <div class="vector-toc-text"> 4.1 International System of Quantities </div> </a> <ul id="toc-International_System_of_Quantities-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Controlling_authority" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Controlling_authority"> <div class="vector-toc-text"> 4.2 Controlling authority </div> </a> <ul id="toc-Controlling_authority-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-History" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#History"> <div class="vector-toc-text"> 5 History </div> </a> <button aria-controls="toc-History-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> Toggle History subsection </button> <ul id="toc-History-sublist" class="vector-toc-list"> <li id="toc-CGS_and_MKS_systems" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#CGS_and_MKS_systems"> <div class="vector-toc-text"> 5.1 CGS and MKS systems </div> </a> <ul id="toc-CGS_and_MKS_systems-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Metre_Convention" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Metre_Convention"> <div class="vector-toc-text"> 5.2 Metre Convention </div> </a> <ul id="toc-Metre_Convention-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Giovanni_Giorgi_and_the_problem_of_electrical_units" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Giovanni_Giorgi_and_the_problem_of_electrical_units"> <div class="vector-toc-text"> 5.3 Giovanni Giorgi and the problem of electrical units </div> </a> <ul id="toc-Giovanni_Giorgi_and_the_problem_of_electrical_units-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-9th_CGPM,_the_precursor_to_SI" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#9th_CGPM,_the_precursor_to_SI"> <div class="vector-toc-text"> 5.4 9th CGPM, the precursor to SI </div> </a> <ul id="toc-9th_CGPM,_the_precursor_to_SI-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Birth_of_the_SI" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Birth_of_the_SI"> <div class="vector-toc-text"> 5.5 Birth of the SI </div> </a> <ul id="toc-Birth_of_the_SI-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-2019_redefinition" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#2019_redefinition"> <div class="vector-toc-text"> 5.6 2019 redefinition </div> </a> <ul id="toc-2019_redefinition-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Related_units" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Related_units"> <div class="vector-toc-text"> 6 Related units </div> </a> <button aria-controls="toc-Related_units-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> Toggle Related units subsection </button> <ul id="toc-Related_units-sublist" class="vector-toc-list"> <li id="toc-Non-SI_units_accepted_for_use_with_SI" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Non-SI_units_accepted_for_use_with_SI"> <div class="vector-toc-text"> 6.1 Non-SI units accepted for use with SI </div> </a> <ul id="toc-Non-SI_units_accepted_for_use_with_SI-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Metric_units_not_recognised_by_SI" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Metric_units_not_recognised_by_SI"> <div class="vector-toc-text"> 6.2 Metric units not recognised by SI </div> </a> <ul id="toc-Metric_units_not_recognised_by_SI-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Unacceptable_uses" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Unacceptable_uses"> <div class="vector-toc-text"> 6.3 Unacceptable uses </div> </a> <ul id="toc-Unacceptable_uses-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> 7 See also </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Notes" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Notes"> <div class="vector-toc-text"> 8 Notes </div> </a> <ul id="toc-Notes-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> 9 References </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Further_reading" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Further_reading"> <div class="vector-toc-text"> 10 Further reading </div> </a> <ul id="toc-Further_reading-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#External_links"> <div class="vector-toc-text"> 11 External links </div> </a> <ul id="toc-External_links-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" > <input type="checkbox" id="vector-page-titlebar-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-titlebar-toc" class="vector-dropdown-checkbox " aria-label="Toggle the table of contents" > <label id="vector-page-titlebar-toc-label" for="vector-page-titlebar-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" > Toggle the table of contents </label> <div class="vector-dropdown-content"> <div id="vector-page-titlebar-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading">International System of Units</h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="Go to an article in another language. Available in 150 languages" > <label id="p-lang-btn-label" for="p-lang-btn-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive mw-portlet-lang-heading-150" aria-hidden="true" > 150 languages </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-af mw-list-item"><a href="https://af.wikipedia.org/wiki/SI-stelsel" title="SI-stelsel – Afrikaans" lang="af" hreflang="af" data-title="SI-stelsel" data-language-autonym="Afrikaans" data-language-local-name="Afrikaans" class="interlanguage-link-target">Afrikaans</a></li><li class="interlanguage-link interwiki-als mw-list-item"><a href="https://als.wikipedia.org/wiki/SI-Einheitensystem" title="SI-Einheitensystem – Alemannic" lang="gsw" hreflang="gsw" data-title="SI-Einheitensystem" data-language-autonym="Alemannisch" data-language-local-name="Alemannic" class="interlanguage-link-target">Alemannisch</a></li><li class="interlanguage-link interwiki-ab mw-list-item"><a href="https://ab.wikipedia.org/wiki/%D0%A1%D0%98" title="СИ – Abkhazian" lang="ab" hreflang="ab" data-title="СИ" data-language-autonym="Аԥсшәа" data-language-local-name="Abkhazian" class="interlanguage-link-target">Аԥсшәа</a></li><li class="interlanguage-link interwiki-ar mw-list-item"><a href="https://ar.wikipedia.org/wiki/%D9%86%D8%B8%D8%A7%D9%85_%D8%A7%D9%84%D9%88%D8%AD%D8%AF%D8%A7%D8%AA_%D8%A7%D9%84%D8%AF%D9%88%D9%84%D9%8A" title="نظام الوحدات الدولي – Arabic" lang="ar" hreflang="ar" data-title="نظام الوحدات الدولي" data-language-autonym="العربية" data-language-local-name="Arabic" class="interlanguage-link-target">العربية</a></li><li class="interlanguage-link interwiki-an mw-list-item"><a href="https://an.wikipedia.org/wiki/Sistema_Internacional_d%27Unidaz" title="Sistema Internacional d'Unidaz – Aragonese" lang="an" hreflang="an" data-title="Sistema Internacional d'Unidaz" data-language-autonym="Aragonés" data-language-local-name="Aragonese" class="interlanguage-link-target">Aragonés</a></li><li class="interlanguage-link interwiki-hyw mw-list-item"><a href="https://hyw.wikipedia.org/wiki/%D5%84%D5%AB%D5%A1%D6%82%D5%B8%D6%80%D5%B6%D5%A5%D6%80%D5%B8%D6%82_%D5%84%D5%AB%D5%BB%D5%A1%D5%A6%D5%A3%D5%A1%D5%B5%D5%AB%D5%B6_%D5%80%D5%A1%D5%B4%D5%A1%D5%AF%D5%A1%D6%80%D5%A3" title="Միաւորներու Միջազգային Համակարգ – Western Armenian" lang="hyw" hreflang="hyw" data-title="Միաւորներու Միջազգային Համակարգ" data-language-autonym="Արեւմտահայերէն" data-language-local-name="Western Armenian" class="interlanguage-link-target">Արեւմտահայերէն</a></li><li class="interlanguage-link interwiki-as mw-list-item"><a href="https://as.wikipedia.org/wiki/%E0%A6%86%E0%A6%A8%E0%A7%8D%E0%A6%A4%E0%A7%B0%E0%A7%8D%E0%A6%9C%E0%A6%BE%E0%A6%A4%E0%A6%BF%E0%A6%95_%E0%A6%8F%E0%A6%95%E0%A6%95_%E0%A6%AA%E0%A6%A6%E0%A7%8D%E0%A6%A7%E0%A6%A4%E0%A6%BF" title="আন্তৰ্জাতিক একক পদ্ধতি – Assamese" lang="as" hreflang="as" data-title="আন্তৰ্জাতিক একক পদ্ধতি" data-language-autonym="অসমীয়া" data-language-local-name="Assamese" class="interlanguage-link-target">অসমীয়া</a></li><li class="interlanguage-link interwiki-ast mw-list-item"><a href="https://ast.wikipedia.org/wiki/Sistema_internacional_d%27unidaes" title="Sistema internacional d'unidaes – Asturian" lang="ast" hreflang="ast" data-title="Sistema internacional d'unidaes" data-language-autonym="Asturianu" data-language-local-name="Asturian" class="interlanguage-link-target">Asturianu</a></li><li class="interlanguage-link interwiki-gn mw-list-item"><a href="https://gn.wikipedia.org/wiki/Ta%27%C3%A3haku%C3%A9ra_Ypykatu_Hetatet%C3%A3gua" title="Ta'ãhakuéra Ypykatu Hetatetãgua – Guarani" lang="gn" hreflang="gn" data-title="Ta'ãhakuéra Ypykatu Hetatetãgua" data-language-autonym="Avañe'ẽ" data-language-local-name="Guarani" class="interlanguage-link-target">Avañe'ẽ</a></li><li class="interlanguage-link interwiki-az mw-list-item"><a href="https://az.wikipedia.org/wiki/Beyn%C9%99lxalq_vahidl%C9%99r_sistemi" title="Beynəlxalq vahidlər sistemi – Azerbaijani" lang="az" hreflang="az" data-title="Beynəlxalq vahidlər sistemi" data-language-autonym="Azərbaycanca" data-language-local-name="Azerbaijani" class="interlanguage-link-target">Azərbaycanca</a></li><li class="interlanguage-link interwiki-azb mw-list-item"><a href="https://azb.wikipedia.org/wiki/%D9%85%DB%8C%D9%84%D8%AA%D9%84%D8%B1%D8%A2%D8%B1%D8%A7%D8%B3%DB%8C_%D8%A8%DB%8C%D8%B1%DB%8C%D9%85%D9%84%D8%B1_%D8%B3%DB%8C%D8%B3%D8%AA%D9%85%DB%8C" title="میلتلرآراسی بیریملر سیستمی – South Azerbaijani" lang="azb" hreflang="azb" data-title="میلتلرآراسی بیریملر سیستمی" data-language-autonym="تۆرکجه" data-language-local-name="South Azerbaijani" class="interlanguage-link-target">تۆرکجه</a></li><li class="interlanguage-link interwiki-bn mw-list-item"><a href="https://bn.wikipedia.org/wiki/%E0%A6%86%E0%A6%A8%E0%A7%8D%E0%A6%A4%E0%A6%B0%E0%A7%8D%E0%A6%9C%E0%A6%BE%E0%A6%A4%E0%A6%BF%E0%A6%95_%E0%A6%8F%E0%A6%95%E0%A6%95_%E0%A6%AA%E0%A6%A6%E0%A7%8D%E0%A6%A7%E0%A6%A4%E0%A6%BF" title="আন্তর্জাতিক একক পদ্ধতি – Bangla" lang="bn" hreflang="bn" data-title="আন্তর্জাতিক একক পদ্ধতি" data-language-autonym="বাংলা" data-language-local-name="Bangla" class="interlanguage-link-target">বাংলা</a></li><li class="interlanguage-link interwiki-zh-min-nan mw-list-item"><a href="https://zh-min-nan.wikipedia.org/wiki/Kok-ch%C3%A8_Tan-%C5%ABi_H%C4%93-th%C3%B3ng" title="Kok-chè Tan-ūi Hē-thóng – Minnan" lang="nan" hreflang="nan" data-title="Kok-chè Tan-ūi Hē-thóng" data-language-autonym="閩南語 / Bân-lâm-gú" data-language-local-name="Minnan" class="interlanguage-link-target">閩南語 / Bân-lâm-gú</a></li><li class="interlanguage-link interwiki-ba mw-list-item"><a href="https://ba.wikipedia.org/wiki/%D0%A5%D0%B0%D0%BB%D1%8B%D2%A1-%D0%B0%D1%80%D0%B0_%D0%B1%D0%B5%D1%80%D3%99%D0%BC%D0%B5%D0%BA%D1%82%D3%99%D1%80_%D1%81%D0%B8%D1%81%D1%82%D0%B5%D0%BC%D0%B0%D2%BB%D1%8B" title="Халыҡ-ара берәмектәр системаһы – Bashkir" lang="ba" hreflang="ba" data-title="Халыҡ-ара берәмектәр системаһы" data-language-autonym="Башҡортса" data-language-local-name="Bashkir" class="interlanguage-link-target">Башҡортса</a></li><li class="interlanguage-link interwiki-be mw-list-item"><a href="https://be.wikipedia.org/wiki/%D0%A1%D0%86_(%D0%BC%D1%96%D0%B6%D0%BD%D0%B0%D1%80%D0%BE%D0%B4%D0%BD%D0%B0%D1%8F_%D1%81%D1%96%D1%81%D1%82%D1%8D%D0%BC%D0%B0_%D0%B0%D0%B4%D0%B7%D1%96%D0%BD%D0%B0%D0%BA_%D0%B2%D1%8B%D0%BC%D1%8F%D1%80%D1%8D%D0%BD%D0%BD%D1%8F)" title="СІ (міжнародная сістэма адзінак вымярэння) – Belarusian" lang="be" hreflang="be" data-title="СІ (міжнародная сістэма адзінак вымярэння)" data-language-autonym="Беларуская" data-language-local-name="Belarusian" class="interlanguage-link-target">Беларуская</a></li><li class="interlanguage-link interwiki-be-x-old mw-list-item"><a href="https://be-tarask.wikipedia.org/wiki/%D0%9C%D1%96%D0%B6%D0%BD%D0%B0%D1%80%D0%BE%D0%B4%D0%BD%D0%B0%D1%8F_%D1%81%D1%8B%D1%81%D1%82%D1%8D%D0%BC%D0%B0_%D0%A1%D0%86" title="Міжнародная сыстэма СІ – Belarusian (Taraškievica orthography)" lang="be-tarask" hreflang="be-tarask" data-title="Міжнародная сыстэма СІ" data-language-autonym="Беларуская (тарашкевіца)" data-language-local-name="Belarusian (Taraškievica orthography)" class="interlanguage-link-target">Беларуская (тарашкевіца)</a></li><li class="interlanguage-link interwiki-bg mw-list-item"><a href="https://bg.wikipedia.org/wiki/%D0%9C%D0%B5%D0%B6%D0%B4%D1%83%D0%BD%D0%B0%D1%80%D0%BE%D0%B4%D0%BD%D0%B0_%D1%81%D0%B8%D1%81%D1%82%D0%B5%D0%BC%D0%B0_%D0%B5%D0%B4%D0%B8%D0%BD%D0%B8%D1%86%D0%B8" title="Международна система единици – Bulgarian" lang="bg" hreflang="bg" data-title="Международна система единици" data-language-autonym="Български" data-language-local-name="Bulgarian" class="interlanguage-link-target">Български</a></li><li class="interlanguage-link interwiki-bs mw-list-item"><a href="https://bs.wikipedia.org/wiki/SI_sistem" title="SI sistem – Bosnian" lang="bs" hreflang="bs" data-title="SI sistem" data-language-autonym="Bosanski" data-language-local-name="Bosnian" class="interlanguage-link-target">Bosanski</a></li><li class="interlanguage-link interwiki-br mw-list-item"><a href="https://br.wikipedia.org/wiki/Reizhiad_unanenno%C3%B9_etrebroadel" title="Reizhiad unanennoù etrebroadel – Breton" lang="br" hreflang="br" data-title="Reizhiad unanennoù etrebroadel" data-language-autonym="Brezhoneg" data-language-local-name="Breton" class="interlanguage-link-target">Brezhoneg</a></li><li class="interlanguage-link interwiki-bxr mw-list-item"><a href="https://bxr.wikipedia.org/wiki/%D0%A3%D0%BB%D0%B0%D1%81%D1%85%D0%BE%D0%BE%D1%80%D0%BE%D0%BD%D0%B4%D1%8B%D0%BD_%D0%BD%D1%8D%D0%B3%D1%8D%D0%B6%D1%8B%D0%BD_%D1%81%D0%B8%D1%81%D1%82%D0%B5%D0%BC%D1%8D" title="Уласхоорондын нэгэжын системэ – Russia Buriat" lang="bxr" hreflang="bxr" data-title="Уласхоорондын нэгэжын системэ" data-language-autonym="Буряад" data-language-local-name="Russia Buriat" class="interlanguage-link-target">Буряад</a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/Sistema_Internacional_d%27Unitats" title="Sistema Internacional d'Unitats – Catalan" lang="ca" hreflang="ca" data-title="Sistema Internacional d'Unitats" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target">Català</a></li><li class="interlanguage-link interwiki-cv mw-list-item"><a href="https://cv.wikipedia.org/wiki/%D0%A1%D0%98_(%D0%92%D0%B8%C3%A7%D0%B5%D0%B2_%D0%BF%C4%95%D1%80%D1%87%D0%B8%D1%81%D0%B5%D0%BD_%D1%82%C4%95%D0%BD%D1%87%D0%B5%D1%80%D0%B8_%D1%82%D1%8B%D1%82%C4%83%D0%BC%C4%95)" title="СИ (Виçев пĕрчисен тĕнчери тытăмĕ) – Chuvash" lang="cv" hreflang="cv" data-title="СИ (Виçев пĕрчисен тĕнчери тытăмĕ)" data-language-autonym="Чӑвашла" data-language-local-name="Chuvash" class="interlanguage-link-target">Чӑвашла</a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/Soustava_SI" title="Soustava SI – Czech" lang="cs" hreflang="cs" data-title="Soustava SI" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target">Čeština</a></li><li class="interlanguage-link interwiki-cy mw-list-item"><a href="https://cy.wikipedia.org/wiki/System_Ryngwladol_o_Unedau" title="System Ryngwladol o Unedau – Welsh" lang="cy" hreflang="cy" data-title="System Ryngwladol o Unedau" data-language-autonym="Cymraeg" data-language-local-name="Welsh" class="interlanguage-link-target">Cymraeg</a></li><li class="interlanguage-link interwiki-da mw-list-item"><a href="https://da.wikipedia.org/wiki/SI-systemet" title="SI-systemet – Danish" lang="da" hreflang="da" data-title="SI-systemet" data-language-autonym="Dansk" data-language-local-name="Danish" class="interlanguage-link-target">Dansk</a></li><li class="interlanguage-link interwiki-ary mw-list-item"><a href="https://ary.wikipedia.org/wiki/%D8%B3%D9%8A%D8%B3%D8%AA%D9%8A%D9%85_%D8%B9%D8%A7%D9%84%D9%85%D9%8A_%D8%AF_%D9%84%D8%B9%D8%A8%D8%B1%D8%A7%D8%AA" title="سيستيم عالمي د لعبرات – Moroccan Arabic" lang="ary" hreflang="ary" data-title="سيستيم عالمي د لعبرات" data-language-autonym="الدارجة" data-language-local-name="Moroccan Arabic" class="interlanguage-link-target">الدارجة</a></li><li class="interlanguage-link interwiki-se mw-list-item"><a href="https://se.wikipedia.org/wiki/SI-systema" title="SI-systema – Northern Sami" lang="se" hreflang="se" data-title="SI-systema" data-language-autonym="Davvisámegiella" data-language-local-name="Northern Sami" class="interlanguage-link-target">Davvisámegiella</a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Internationales_Einheitensystem" title="Internationales Einheitensystem – German" lang="de" hreflang="de" data-title="Internationales Einheitensystem" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target">Deutsch</a></li><li class="interlanguage-link interwiki-et mw-list-item"><a href="https://et.wikipedia.org/wiki/SI" title="SI – Estonian" lang="et" hreflang="et" data-title="SI" data-language-autonym="Eesti" data-language-local-name="Estonian" class="interlanguage-link-target">Eesti</a></li><li class="interlanguage-link interwiki-el mw-list-item"><a href="https://el.wikipedia.org/wiki/%CE%94%CE%B9%CE%B5%CE%B8%CE%BD%CE%AD%CF%82_%CF%83%CF%8D%CF%83%CF%84%CE%B7%CE%BC%CE%B1_%CE%BC%CE%BF%CE%BD%CE%AC%CE%B4%CF%89%CE%BD" title="Διεθνές σύστημα μονάδων – Greek" lang="el" hreflang="el" data-title="Διεθνές σύστημα μονάδων" data-language-autonym="Ελληνικά" data-language-local-name="Greek" class="interlanguage-link-target">Ελληνικά</a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Sistema_Internacional_de_Unidades" title="Sistema Internacional de Unidades – Spanish" lang="es" hreflang="es" data-title="Sistema Internacional de Unidades" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target">Español</a></li><li class="interlanguage-link interwiki-eo mw-list-item"><a href="https://eo.wikipedia.org/wiki/Internacia_sistemo_de_unuoj" title="Internacia sistemo de unuoj – Esperanto" lang="eo" hreflang="eo" data-title="Internacia sistemo de unuoj" data-language-autonym="Esperanto" data-language-local-name="Esperanto" class="interlanguage-link-target">Esperanto</a></li><li class="interlanguage-link interwiki-eu mw-list-item"><a href="https://eu.wikipedia.org/wiki/Nazioarteko_Unitate_Sistema" title="Nazioarteko Unitate Sistema – Basque" lang="eu" hreflang="eu" data-title="Nazioarteko Unitate Sistema" data-language-autonym="Euskara" data-language-local-name="Basque" class="interlanguage-link-target">Euskara</a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%D8%AF%D8%B3%D8%AA%DA%AF%D8%A7%D9%87_%D8%A8%DB%8C%D9%86%E2%80%8C%D8%A7%D9%84%D9%85%D9%84%D9%84%DB%8C_%DB%8C%DA%A9%D8%A7%D9%87%D8%A7" title="دستگاه بین‌المللی یکاها – Persian" lang="fa" hreflang="fa" data-title="دستگاه بین‌المللی یکاها" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target">فارسی</a></li><li class="interlanguage-link interwiki-hif mw-list-item"><a href="https://hif.wikipedia.org/wiki/SI" title="SI – Fiji Hindi" lang="hif" hreflang="hif" data-title="SI" data-language-autonym="Fiji Hindi" data-language-local-name="Fiji Hindi" class="interlanguage-link-target">Fiji Hindi</a></li><li class="interlanguage-link interwiki-fo mw-list-item"><a href="https://fo.wikipedia.org/wiki/Millumtj%C3%B3%C3%B0a_eindarskipanin" title="Millumtjóða eindarskipanin – Faroese" lang="fo" hreflang="fo" data-title="Millumtjóða eindarskipanin" data-language-autonym="Føroyskt" data-language-local-name="Faroese" class="interlanguage-link-target">Føroyskt</a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/Syst%C3%A8me_international_d%27unit%C3%A9s" title="Système international d'unités – French" lang="fr" hreflang="fr" data-title="Système international d'unités" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target">Français</a></li><li class="interlanguage-link interwiki-fy mw-list-item"><a href="https://fy.wikipedia.org/wiki/Ynternasjonaal_Systeem_fan_Ienheden" title="Ynternasjonaal Systeem fan Ienheden – Western Frisian" lang="fy" hreflang="fy" data-title="Ynternasjonaal Systeem fan Ienheden" data-language-autonym="Frysk" data-language-local-name="Western Frisian" class="interlanguage-link-target">Frysk</a></li><li class="interlanguage-link interwiki-fur mw-list-item"><a href="https://fur.wikipedia.org/wiki/Sisteme_internazion%C3%A2l_di_unit%C3%A2ts" title="Sisteme internazionâl di unitâts – Friulian" lang="fur" hreflang="fur" data-title="Sisteme internazionâl di unitâts" data-language-autonym="Furlan" data-language-local-name="Friulian" class="interlanguage-link-target">Furlan</a></li><li class="interlanguage-link interwiki-ga mw-list-item"><a href="https://ga.wikipedia.org/wiki/C%C3%B3ras_Idirn%C3%A1isi%C3%BAnta_na_nAonad" title="Córas Idirnáisiúnta na nAonad – Irish" lang="ga" hreflang="ga" data-title="Córas Idirnáisiúnta na nAonad" data-language-autonym="Gaeilge" data-language-local-name="Irish" class="interlanguage-link-target">Gaeilge</a></li><li class="interlanguage-link interwiki-gd mw-list-item"><a href="https://gd.wikipedia.org/wiki/Siostam_Eadar-n%C3%A0iseanta_nan_Aonadan" title="Siostam Eadar-nàiseanta nan Aonadan – Scottish Gaelic" lang="gd" hreflang="gd" data-title="Siostam Eadar-nàiseanta nan Aonadan" data-language-autonym="Gàidhlig" data-language-local-name="Scottish Gaelic" class="interlanguage-link-target">Gàidhlig</a></li><li class="interlanguage-link interwiki-gl mw-list-item"><a href="https://gl.wikipedia.org/wiki/Sistema_Internacional_de_Unidades" title="Sistema Internacional de Unidades – Galician" lang="gl" hreflang="gl" data-title="Sistema Internacional de Unidades" data-language-autonym="Galego" data-language-local-name="Galician" class="interlanguage-link-target">Galego</a></li><li class="interlanguage-link interwiki-gan mw-list-item"><a href="https://gan.wikipedia.org/wiki/%E5%9C%8B%E9%9A%9B%E5%96%AE%E4%BD%8D%E7%B3%BB%E7%B5%B1" title="國際單位系統 – Gan" lang="gan" hreflang="gan" data-title="國際單位系統" data-language-autonym="贛語" data-language-local-name="Gan" class="interlanguage-link-target">贛語</a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/%EA%B5%AD%EC%A0%9C%EB%8B%A8%EC%9C%84%EA%B3%84" title="국제단위계 – Korean" lang="ko" hreflang="ko" data-title="국제단위계" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target">한국어</a></li><li class="interlanguage-link interwiki-hy mw-list-item"><a href="https://hy.wikipedia.org/wiki/%D5%84%D5%AB%D5%A1%D5%BE%D5%B8%D6%80%D5%B6%D5%A5%D6%80%D5%AB_%D5%B4%D5%AB%D5%BB%D5%A1%D5%A6%D5%A3%D5%A1%D5%B5%D5%AB%D5%B6_%D5%B0%D5%A1%D5%B4%D5%A1%D5%AF%D5%A1%D6%80%D5%A3" title="Միավորների միջազգային համակարգ – Armenian" lang="hy" hreflang="hy" data-title="Միավորների միջազգային համակարգ" data-language-autonym="Հայերեն" data-language-local-name="Armenian" class="interlanguage-link-target">Հայերեն</a></li><li class="interlanguage-link interwiki-hi mw-list-item"><a href="https://hi.wikipedia.org/wiki/%E0%A4%85%E0%A4%A8%E0%A5%8D%E0%A4%A4%E0%A4%B0%E0%A4%B0%E0%A4%BE%E0%A4%B7%E0%A5%8D%E0%A4%9F%E0%A5%8D%E0%A4%B0%E0%A5%80%E0%A4%AF_%E0%A4%AE%E0%A4%BE%E0%A4%A4%E0%A5%8D%E0%A4%B0%E0%A4%95_%E0%A4%AA%E0%A5%8D%E0%A4%B0%E0%A4%A3%E0%A4%BE%E0%A4%B2%E0%A5%80" title="अन्तरराष्ट्रीय मात्रक प्रणाली – Hindi" lang="hi" hreflang="hi" data-title="अन्तरराष्ट्रीय मात्रक प्रणाली" data-language-autonym="हिन्दी" data-language-local-name="Hindi" class="interlanguage-link-target">हिन्दी</a></li><li class="interlanguage-link interwiki-hr mw-list-item"><a href="https://hr.wikipedia.org/wiki/Me%C4%91unarodni_sustav_mjernih_jedinica" title="Međunarodni sustav mjernih jedinica – Croatian" lang="hr" hreflang="hr" data-title="Međunarodni sustav mjernih jedinica" data-language-autonym="Hrvatski" data-language-local-name="Croatian" class="interlanguage-link-target">Hrvatski</a></li><li class="interlanguage-link interwiki-io mw-list-item"><a href="https://io.wikipedia.org/wiki/Internaciona_Sistemo_di_Unaji" title="Internaciona Sistemo di Unaji – Ido" lang="io" hreflang="io" data-title="Internaciona Sistemo di Unaji" data-language-autonym="Ido" data-language-local-name="Ido" class="interlanguage-link-target">Ido</a></li><li class="interlanguage-link interwiki-ilo mw-list-item"><a href="https://ilo.wikipedia.org/wiki/Internasional_a_Sistema_dagiti_Yunit" title="Internasional a Sistema dagiti Yunit – Iloko" lang="ilo" hreflang="ilo" data-title="Internasional a Sistema dagiti Yunit" data-language-autonym="Ilokano" data-language-local-name="Iloko" class="interlanguage-link-target">Ilokano</a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Sistem_Satuan_Internasional" title="Sistem Satuan Internasional – Indonesian" lang="id" hreflang="id" data-title="Sistem Satuan Internasional" data-language-autonym="Bahasa Indonesia" data-language-local-name="Indonesian" class="interlanguage-link-target">Bahasa Indonesia</a></li><li class="interlanguage-link interwiki-ia mw-list-item"><a href="https://ia.wikipedia.org/wiki/Systema_International_de_Unitates" title="Systema International de Unitates – Interlingua" lang="ia" hreflang="ia" data-title="Systema International de Unitates" data-language-autonym="Interlingua" data-language-local-name="Interlingua" class="interlanguage-link-target">Interlingua</a></li><li class="interlanguage-link interwiki-ie mw-list-item"><a href="https://ie.wikipedia.org/wiki/Sistema_International_de_Unit%C3%A9s" title="Sistema International de Unités – Interlingue" lang="ie" hreflang="ie" data-title="Sistema International de Unités" data-language-autonym="Interlingue" data-language-local-name="Interlingue" class="interlanguage-link-target">Interlingue</a></li><li class="interlanguage-link interwiki-xh mw-list-item"><a href="https://xh.wikipedia.org/wiki/Inkqubo_yamazwe_ngamazwe_yeeyunithi_zokulinganisa" title="Inkqubo yamazwe ngamazwe yeeyunithi zokulinganisa – Xhosa" lang="xh" hreflang="xh" data-title="Inkqubo yamazwe ngamazwe yeeyunithi zokulinganisa" data-language-autonym="IsiXhosa" data-language-local-name="Xhosa" class="interlanguage-link-target">IsiXhosa</a></li><li class="interlanguage-link interwiki-is mw-list-item"><a href="https://is.wikipedia.org/wiki/Al%C3%BEj%C3%B3%C3%B0lega_einingakerfi%C3%B0" title="Alþjóðlega einingakerfið – Icelandic" lang="is" hreflang="is" data-title="Alþjóðlega einingakerfið" data-language-autonym="Íslenska" data-language-local-name="Icelandic" class="interlanguage-link-target">Íslenska</a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Sistema_internazionale_di_unit%C3%A0_di_misura" title="Sistema internazionale di unità di misura – Italian" lang="it" hreflang="it" data-title="Sistema internazionale di unità di misura" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target">Italiano</a></li><li class="interlanguage-link interwiki-he mw-list-item"><a href="https://he.wikipedia.org/wiki/%D7%9E%D7%A2%D7%A8%D7%9B%D7%AA_%D7%94%D7%99%D7%97%D7%99%D7%93%D7%95%D7%AA_%D7%94%D7%91%D7%99%D7%9F-%D7%9C%D7%90%D7%95%D7%9E%D7%99%D7%AA" title="מערכת היחידות הבין-לאומית – Hebrew" lang="he" hreflang="he" data-title="מערכת היחידות הבין-לאומית" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target">עברית</a></li><li class="interlanguage-link interwiki-jv mw-list-item"><a href="https://jv.wikipedia.org/wiki/Sistem_P%C3%A9tungan_Internasional" title="Sistem Pétungan Internasional – Javanese" lang="jv" hreflang="jv" data-title="Sistem Pétungan Internasional" data-language-autonym="Jawa" data-language-local-name="Javanese" class="interlanguage-link-target">Jawa</a></li><li class="interlanguage-link interwiki-kn mw-list-item"><a href="https://kn.wikipedia.org/wiki/%E0%B2%85%E0%B2%82%E0%B2%A4%E0%B2%B0%E0%B2%B0%E0%B2%BE%E0%B2%B7%E0%B3%8D%E0%B2%9F%E0%B3%8D%E0%B2%B0%E0%B3%80%E0%B2%AF_%E0%B2%8F%E0%B2%95%E0%B2%AE%E0%B2%BE%E0%B2%A8_%E0%B2%B5%E0%B3%8D%E0%B2%AF%E0%B2%B5%E0%B2%B8%E0%B3%8D%E0%B2%A5%E0%B3%86" title="ಅಂತರರಾಷ್ಟ್ರೀಯ ಏಕಮಾನ ವ್ಯವಸ್ಥೆ – Kannada" lang="kn" hreflang="kn" data-title="ಅಂತರರಾಷ್ಟ್ರೀಯ ಏಕಮಾನ ವ್ಯವಸ್ಥೆ" data-language-autonym="ಕನ್ನಡ" data-language-local-name="Kannada" class="interlanguage-link-target">ಕನ್ನಡ</a></li><li class="interlanguage-link interwiki-krc badge-Q17437798 badge-goodarticle mw-list-item" title="good article badge"><a href="https://krc.wikipedia.org/wiki/%D0%81%D0%A1" title="ЁС – Karachay-Balkar" lang="krc" hreflang="krc" data-title="ЁС" data-language-autonym="Къарачай-малкъар" data-language-local-name="Karachay-Balkar" class="interlanguage-link-target">Къарачай-малкъар</a></li><li class="interlanguage-link interwiki-ka mw-list-item"><a href="https://ka.wikipedia.org/wiki/%E1%83%94%E1%83%A0%E1%83%97%E1%83%94%E1%83%A3%E1%83%9A%E1%83%97%E1%83%90_%E1%83%A1%E1%83%90%E1%83%94%E1%83%A0%E1%83%97%E1%83%90%E1%83%A8%E1%83%9D%E1%83%A0%E1%83%98%E1%83%A1%E1%83%9D_%E1%83%A1%E1%83%98%E1%83%A1%E1%83%A2%E1%83%94%E1%83%9B%E1%83%90" title="ერთეულთა საერთაშორისო სისტემა – Georgian" lang="ka" hreflang="ka" data-title="ერთეულთა საერთაშორისო სისტემა" data-language-autonym="ქართული" data-language-local-name="Georgian" class="interlanguage-link-target">ქართული</a></li><li class="interlanguage-link interwiki-kk mw-list-item"><a href="https://kk.wikipedia.org/wiki/%D0%A5%D0%B0%D0%BB%D1%8B%D2%9B%D0%B0%D1%80%D0%B0%D0%BB%D1%8B%D2%9B_%D0%B1%D1%96%D1%80%D0%BB%D1%96%D0%BA%D1%82%D0%B5%D1%80_%D0%B6%D2%AF%D0%B9%D0%B5%D1%81%D1%96" title="Халықаралық бірліктер жүйесі – Kazakh" lang="kk" hreflang="kk" data-title="Халықаралық бірліктер жүйесі" data-language-autonym="Қазақша" data-language-local-name="Kazakh" class="interlanguage-link-target">Қазақша</a></li><li class="interlanguage-link interwiki-kw mw-list-item"><a href="https://kw.wikipedia.org/wiki/Kevreyth_Keswlasek_Unsesow" title="Kevreyth Keswlasek Unsesow – Cornish" lang="kw" hreflang="kw" data-title="Kevreyth Keswlasek Unsesow" data-language-autonym="Kernowek" data-language-local-name="Cornish" class="interlanguage-link-target">Kernowek</a></li><li class="interlanguage-link interwiki-sw mw-list-item"><a href="https://sw.wikipedia.org/wiki/Vipimo_sanifu_vya_kimataifa" title="Vipimo sanifu vya kimataifa – Swahili" lang="sw" hreflang="sw" data-title="Vipimo sanifu vya kimataifa" data-language-autonym="Kiswahili" data-language-local-name="Swahili" class="interlanguage-link-target">Kiswahili</a></li><li class="interlanguage-link interwiki-ht mw-list-item"><a href="https://ht.wikipedia.org/wiki/Sist%C3%A8m_ent%C3%A8nasyonal_inite" title="Sistèm entènasyonal inite – Haitian Creole" lang="ht" hreflang="ht" data-title="Sistèm entènasyonal inite" data-language-autonym="Kreyòl ayisyen" data-language-local-name="Haitian Creole" class="interlanguage-link-target">Kreyòl ayisyen</a></li><li class="interlanguage-link interwiki-gcr mw-list-item"><a href="https://gcr.wikipedia.org/wiki/Sist%C3%A8m_enternasyonal_di_init%C3%A9" title="Sistèm enternasyonal di inité – Guianan Creole" lang="gcr" hreflang="gcr" data-title="Sistèm enternasyonal di inité" data-language-autonym="Kriyòl gwiyannen" data-language-local-name="Guianan Creole" class="interlanguage-link-target">Kriyòl gwiyannen</a></li><li class="interlanguage-link interwiki-ku mw-list-item"><a href="https://ku.wikipedia.org/wiki/Pergala_Navnetewey%C3%AE_ya_Yekeyan" title="Pergala Navneteweyî ya Yekeyan – Kurdish" lang="ku" hreflang="ku" data-title="Pergala Navneteweyî ya Yekeyan" data-language-autonym="Kurdî" data-language-local-name="Kurdish" class="interlanguage-link-target">Kurdî</a></li><li class="interlanguage-link interwiki-ky mw-list-item"><a href="https://ky.wikipedia.org/wiki/%D0%AD%D0%BB_%D0%B0%D1%80%D0%B0%D0%BB%D1%8B%D0%BA_%D0%B1%D0%B8%D1%80%D0%B4%D0%B8%D0%BA%D1%82%D0%B5%D1%80_%D1%81%D0%B8%D1%81%D1%82%D0%B5%D0%BC%D0%B0%D1%81%D1%8B" title="Эл аралык бирдиктер системасы – Kyrgyz" lang="ky" hreflang="ky" data-title="Эл аралык бирдиктер системасы" data-language-autonym="Кыргызча" data-language-local-name="Kyrgyz" class="interlanguage-link-target">Кыргызча</a></li><li class="interlanguage-link interwiki-la mw-list-item"><a href="https://la.wikipedia.org/wiki/Systema_internationale_unitatum" title="Systema internationale unitatum – Latin" lang="la" hreflang="la" data-title="Systema internationale unitatum" data-language-autonym="Latina" data-language-local-name="Latin" class="interlanguage-link-target">Latina</a></li><li class="interlanguage-link interwiki-lv mw-list-item"><a href="https://lv.wikipedia.org/wiki/Starptautisk%C4%81_m%C4%93rvien%C4%ABbu_sist%C4%93ma" title="Starptautiskā mērvienību sistēma – Latvian" lang="lv" hreflang="lv" data-title="Starptautiskā mērvienību sistēma" data-language-autonym="Latviešu" data-language-local-name="Latvian" class="interlanguage-link-target">Latviešu</a></li><li class="interlanguage-link interwiki-lb mw-list-item"><a href="https://lb.wikipedia.org/wiki/Internationalen_Eenheetesystem" title="Internationalen Eenheetesystem – Luxembourgish" lang="lb" hreflang="lb" data-title="Internationalen Eenheetesystem" data-language-autonym="Lëtzebuergesch" data-language-local-name="Luxembourgish" class="interlanguage-link-target">Lëtzebuergesch</a></li><li class="interlanguage-link interwiki-lt mw-list-item"><a href="https://lt.wikipedia.org/wiki/SI_(sistema)" title="SI (sistema) – Lithuanian" lang="lt" hreflang="lt" data-title="SI (sistema)" data-language-autonym="Lietuvių" data-language-local-name="Lithuanian" class="interlanguage-link-target">Lietuvių</a></li><li class="interlanguage-link interwiki-li mw-list-item"><a href="https://li.wikipedia.org/wiki/SI" title="SI – Limburgish" lang="li" hreflang="li" data-title="SI" data-language-autonym="Limburgs" data-language-local-name="Limburgish" class="interlanguage-link-target">Limburgs</a></li><li class="interlanguage-link interwiki-lfn mw-list-item"><a href="https://lfn.wikipedia.org/wiki/Sistem_Internasional_de_Unias" title="Sistem Internasional de Unias – Lingua Franca Nova" lang="lfn" hreflang="lfn" data-title="Sistem Internasional de Unias" data-language-autonym="Lingua Franca Nova" data-language-local-name="Lingua Franca Nova" class="interlanguage-link-target">Lingua Franca Nova</a></li><li class="interlanguage-link interwiki-jbo mw-list-item"><a href="https://jbo.wikipedia.org/wiki/treci%27e" title="treci'e – Lojban" lang="jbo" hreflang="jbo" data-title="treci'e" data-language-autonym="La .lojban." data-language-local-name="Lojban" class="interlanguage-link-target">La .lojban.</a></li><li class="interlanguage-link interwiki-lmo mw-list-item"><a href="https://lmo.wikipedia.org/wiki/Sistema_internazional_d%27unitaa" title="Sistema internazional d'unitaa – Lombard" lang="lmo" hreflang="lmo" data-title="Sistema internazional d'unitaa" data-language-autonym="Lombard" data-language-local-name="Lombard" class="interlanguage-link-target">Lombard</a></li><li class="interlanguage-link interwiki-hu mw-list-item"><a href="https://hu.wikipedia.org/wiki/SI-m%C3%A9rt%C3%A9kegys%C3%A9grendszer" title="SI-mértékegységrendszer – Hungarian" lang="hu" hreflang="hu" data-title="SI-mértékegységrendszer" data-language-autonym="Magyar" data-language-local-name="Hungarian" class="interlanguage-link-target">Magyar</a></li><li class="interlanguage-link interwiki-mk mw-list-item"><a href="https://mk.wikipedia.org/wiki/%D0%9C%D0%B5%D1%93%D1%83%D0%BD%D0%B0%D1%80%D0%BE%D0%B4%D0%B5%D0%BD_%D1%81%D0%B8%D1%81%D1%82%D0%B5%D0%BC_%D0%BD%D0%B0_%D0%BC%D0%B5%D1%80%D0%BD%D0%B8_%D0%B5%D0%B4%D0%B8%D0%BD%D0%B8%D1%86%D0%B8" title="Меѓународен систем на мерни единици – Macedonian" lang="mk" hreflang="mk" data-title="Меѓународен систем на мерни единици" data-language-autonym="Македонски" data-language-local-name="Macedonian" class="interlanguage-link-target">Македонски</a></li><li class="interlanguage-link interwiki-ml mw-list-item"><a href="https://ml.wikipedia.org/wiki/%E0%B4%85%E0%B4%A8%E0%B5%8D%E0%B4%A4%E0%B4%BE%E0%B4%B0%E0%B4%BE%E0%B4%B7%E0%B5%8D%E0%B4%9F%E0%B5%8D%E0%B4%B0_%E0%B4%8F%E0%B4%95%E0%B4%95%E0%B4%B5%E0%B5%8D%E0%B4%AF%E0%B4%B5%E0%B4%B8%E0%B5%8D%E0%B4%A5" title="അന്താരാഷ്ട്ര ഏകകവ്യവസ്ഥ – Malayalam" lang="ml" hreflang="ml" data-title="അന്താരാഷ്ട്ര ഏകകവ്യവസ്ഥ" data-language-autonym="മലയാളം" data-language-local-name="Malayalam" class="interlanguage-link-target">മലയാളം</a></li><li class="interlanguage-link interwiki-mt mw-list-item"><a href="https://mt.wikipedia.org/wiki/Sistema_Internazzjonali_ta%27_Unitajiet" title="Sistema Internazzjonali ta' Unitajiet – Maltese" lang="mt" hreflang="mt" data-title="Sistema Internazzjonali ta' Unitajiet" data-language-autonym="Malti" data-language-local-name="Maltese" class="interlanguage-link-target">Malti</a></li><li class="interlanguage-link interwiki-mr mw-list-item"><a href="https://mr.wikipedia.org/wiki/%E0%A4%8F%E0%A4%B8.%E0%A4%86%E0%A4%AF." title="एस.आय. – Marathi" lang="mr" hreflang="mr" data-title="एस.आय." data-language-autonym="मराठी" data-language-local-name="Marathi" class="interlanguage-link-target">मराठी</a></li><li class="interlanguage-link interwiki-arz mw-list-item"><a href="https://arz.wikipedia.org/wiki/%D8%A7%D9%84%D9%86%D8%B8%D8%A7%D9%85_%D8%A7%D9%84%D8%AF%D9%88%D9%84%D9%89_%D9%84%D9%84%D9%88%D8%AD%D8%AF%D8%A7%D8%AA" title="النظام الدولى للوحدات – Egyptian Arabic" lang="arz" hreflang="arz" data-title="النظام الدولى للوحدات" data-language-autonym="مصرى" data-language-local-name="Egyptian Arabic" class="interlanguage-link-target">مصرى</a></li><li class="interlanguage-link interwiki-ms mw-list-item"><a href="https://ms.wikipedia.org/wiki/Sistem_Unit_Antarabangsa" title="Sistem Unit Antarabangsa – Malay" lang="ms" hreflang="ms" data-title="Sistem Unit Antarabangsa" data-language-autonym="Bahasa Melayu" data-language-local-name="Malay" class="interlanguage-link-target">Bahasa Melayu</a></li><li class="interlanguage-link interwiki-mn mw-list-item"><a href="https://mn.wikipedia.org/wiki/%D0%9E%D0%BB%D0%BE%D0%BD_%D1%83%D0%BB%D1%81%D1%8B%D0%BD_%D0%BD%D1%8D%D0%B3%D0%B6%D0%B8%D0%B9%D0%BD_%D1%81%D0%B8%D1%81%D1%82%D0%B5%D0%BC" title="Олон улсын нэгжийн систем – Mongolian" lang="mn" hreflang="mn" data-title="Олон улсын нэгжийн систем" data-language-autonym="Монгол" data-language-local-name="Mongolian" class="interlanguage-link-target">Монгол</a></li><li class="interlanguage-link interwiki-my mw-list-item"><a href="https://my.wikipedia.org/wiki/%E1%80%A1%E1%80%95%E1%80%BC%E1%80%8A%E1%80%BA%E1%80%95%E1%80%BC%E1%80%8A%E1%80%BA%E1%80%86%E1%80%AD%E1%80%AF%E1%80%84%E1%80%BA%E1%80%9B%E1%80%AC_%E1%80%9A%E1%80%B0%E1%80%94%E1%80%85%E1%80%BA%E1%80%85%E1%80%94%E1%80%85%E1%80%BA" title="အပြည်ပြည်ဆိုင်ရာ ယူနစ်စနစ် – Burmese" lang="my" hreflang="my" data-title="အပြည်ပြည်ဆိုင်ရာ ယူနစ်စနစ်" data-language-autonym="မြန်မာဘာသာ" data-language-local-name="Burmese" class="interlanguage-link-target">မြန်မာဘာသာ</a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/SI-stelsel" title="SI-stelsel – Dutch" lang="nl" hreflang="nl" data-title="SI-stelsel" data-language-autonym="Nederlands" data-language-local-name="Dutch" class="interlanguage-link-target">Nederlands</a></li><li class="interlanguage-link interwiki-ne mw-list-item"><a href="https://ne.wikipedia.org/wiki/%E0%A4%85%E0%A4%A8%E0%A5%8D%E0%A4%A4%E0%A4%B0%E0%A5%8D%E0%A4%B0%E0%A4%BE%E0%A4%B7%E0%A5%8D%E0%A4%9F%E0%A5%8D%E0%A4%B0%E0%A5%80%E0%A4%AF_%E0%A4%AE%E0%A4%BE%E0%A4%A4%E0%A5%8D%E0%A4%B0%E0%A4%95_%E0%A4%AA%E0%A5%8D%E0%A4%B0%E0%A4%A3%E0%A4%BE%E0%A4%B2%E0%A5%80" title="अन्तर्राष्ट्रीय मात्रक प्रणाली – Nepali" lang="ne" hreflang="ne" data-title="अन्तर्राष्ट्रीय मात्रक प्रणाली" data-language-autonym="नेपाली" data-language-local-name="Nepali" class="interlanguage-link-target">नेपाली</a></li><li class="interlanguage-link interwiki-new mw-list-item"><a href="https://new.wikipedia.org/wiki/%E0%A4%8F%E0%A4%B8%E0%A5%8D_%E0%A4%86%E0%A4%87" title="एस् आइ – Newari" lang="new" hreflang="new" data-title="एस् आइ" data-language-autonym="नेपाल भाषा" data-language-local-name="Newari" class="interlanguage-link-target">नेपाल भाषा</a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/%E5%9B%BD%E9%9A%9B%E5%8D%98%E4%BD%8D%E7%B3%BB" title="国際単位系 – Japanese" lang="ja" hreflang="ja" data-title="国際単位系" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target">日本語</a></li><li class="interlanguage-link interwiki-frr mw-list-item"><a href="https://frr.wikipedia.org/wiki/SI-s%C3%BCsteem" title="SI-süsteem – Northern Frisian" lang="frr" hreflang="frr" data-title="SI-süsteem" data-language-autonym="Nordfriisk" data-language-local-name="Northern Frisian" class="interlanguage-link-target">Nordfriisk</a></li><li class="interlanguage-link interwiki-no mw-list-item"><a href="https://no.wikipedia.org/wiki/SI-systemet" title="SI-systemet – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="SI-systemet" data-language-autonym="Norsk bokmål" data-language-local-name="Norwegian Bokmål" class="interlanguage-link-target">Norsk bokmål</a></li><li class="interlanguage-link interwiki-nn mw-list-item"><a href="https://nn.wikipedia.org/wiki/SI-systemet" title="SI-systemet – Norwegian Nynorsk" lang="nn" hreflang="nn" data-title="SI-systemet" data-language-autonym="Norsk nynorsk" data-language-local-name="Norwegian Nynorsk" class="interlanguage-link-target">Norsk nynorsk</a></li><li class="interlanguage-link interwiki-oc mw-list-item"><a href="https://oc.wikipedia.org/wiki/Sist%C3%A8ma_Internacionau_d%27Unitats" title="Sistèma Internacionau d'Unitats – Occitan" lang="oc" hreflang="oc" data-title="Sistèma Internacionau d'Unitats" data-language-autonym="Occitan" data-language-local-name="Occitan" class="interlanguage-link-target">Occitan</a></li><li class="interlanguage-link interwiki-uz mw-list-item"><a href="https://uz.wikipedia.org/wiki/Xalqaro_birliklar_tizimi" title="Xalqaro birliklar tizimi – Uzbek" lang="uz" hreflang="uz" data-title="Xalqaro birliklar tizimi" data-language-autonym="Oʻzbekcha / ўзбекча" data-language-local-name="Uzbek" class="interlanguage-link-target">Oʻzbekcha / ўзбекча</a></li><li class="interlanguage-link interwiki-pa mw-list-item"><a href="https://pa.wikipedia.org/wiki/%E0%A8%85%E0%A9%B0%E0%A8%A4%E0%A8%B0%E0%A8%B0%E0%A8%BE%E0%A8%B8%E0%A8%BC%E0%A8%9F%E0%A8%B0%E0%A9%80_%E0%A8%87%E0%A8%95%E0%A8%BE%E0%A8%88_%E0%A8%AA%E0%A9%8D%E0%A8%B0%E0%A8%A3%E0%A8%BE%E0%A8%B2%E0%A9%80" title="ਅੰਤਰਰਾਸ਼ਟਰੀ ਇਕਾਈ ਪ੍ਰਣਾਲੀ – Punjabi" lang="pa" hreflang="pa" data-title="ਅੰਤਰਰਾਸ਼ਟਰੀ ਇਕਾਈ ਪ੍ਰਣਾਲੀ" data-language-autonym="ਪੰਜਾਬੀ" data-language-local-name="Punjabi" class="interlanguage-link-target">ਪੰਜਾਬੀ</a></li><li class="interlanguage-link interwiki-pnb mw-list-item"><a href="https://pnb.wikipedia.org/wiki/%D8%A7%DA%A9%D8%A7%D8%A6%DB%8C%D8%A7%DA%BA_%D8%AF%D8%A7_%D8%B9%D8%A7%D9%84%D9%85%DB%8C_%D9%86%D8%B8%D8%A7%D9%85" title="اکائیاں دا عالمی نظام – Western Punjabi" lang="pnb" hreflang="pnb" data-title="اکائیاں دا عالمی نظام" data-language-autonym="پنجابی" data-language-local-name="Western Punjabi" class="interlanguage-link-target">پنجابی</a></li><li class="interlanguage-link interwiki-ps mw-list-item"><a href="https://ps.wikipedia.org/wiki/%D8%AF_%D9%88%D8%A7%D8%AD%D8%AF%D9%88%D9%86%D9%88_%D9%86%DA%93%D9%8A%D9%88%D8%A7%D9%84_%D8%B3%D9%8A%D8%B3%D8%AA%D9%85" title="د واحدونو نړيوال سيستم – Pashto" lang="ps" hreflang="ps" data-title="د واحدونو نړيوال سيستم" data-language-autonym="پښتو" data-language-local-name="Pashto" class="interlanguage-link-target">پښتو</a></li><li class="interlanguage-link interwiki-jam mw-list-item"><a href="https://jam.wikipedia.org/wiki/Intanashinal_Sistim_a_Yuunit" title="Intanashinal Sistim a Yuunit – Jamaican Creole English" lang="jam" hreflang="jam" data-title="Intanashinal Sistim a Yuunit" data-language-autonym="Patois" data-language-local-name="Jamaican Creole English" class="interlanguage-link-target">Patois</a></li><li class="interlanguage-link interwiki-km mw-list-item"><a href="https://km.wikipedia.org/wiki/%E1%9E%94%E1%9F%92%E1%9E%9A%E1%9E%96%E1%9F%90%E1%9E%93%E1%9F%92%E1%9E%92%E1%9E%81%E1%9F%92%E1%9E%93%E1%9E%B6%E1%9E%8F%E1%9E%A2%E1%9E%93%E1%9F%92%E1%9E%8F%E1%9E%9A%E1%9E%87%E1%9E%B6%E1%9E%8F%E1%9E%B7" title="ប្រព័ន្ធខ្នាតអន្តរជាតិ – Khmer" lang="km" hreflang="km" data-title="ប្រព័ន្ធខ្នាតអន្តរជាតិ" data-language-autonym="ភាសាខ្មែរ" data-language-local-name="Khmer" class="interlanguage-link-target">ភាសាខ្មែរ</a></li><li class="interlanguage-link interwiki-nds mw-list-item"><a href="https://nds.wikipedia.org/wiki/Internatschonal_Eenheitensystem" title="Internatschonal Eenheitensystem – Low German" lang="nds" hreflang="nds" data-title="Internatschonal Eenheitensystem" data-language-autonym="Plattdüütsch" data-language-local-name="Low German" class="interlanguage-link-target">Plattdüütsch</a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Uk%C5%82ad_SI" title="Układ SI – Polish" lang="pl" hreflang="pl" data-title="Układ SI" data-language-autonym="Polski" data-language-local-name="Polish" class="interlanguage-link-target">Polski</a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/Sistema_Internacional_de_Unidades" title="Sistema Internacional de Unidades – Portuguese" lang="pt" hreflang="pt" data-title="Sistema Internacional de Unidades" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target">Português</a></li><li class="interlanguage-link interwiki-ksh mw-list-item"><a href="https://ksh.wikipedia.org/wiki/SI-Basiseinheite" title="SI-Basiseinheite – Colognian" lang="ksh" hreflang="ksh" data-title="SI-Basiseinheite" data-language-autonym="Ripoarisch" data-language-local-name="Colognian" class="interlanguage-link-target">Ripoarisch</a></li><li class="interlanguage-link interwiki-ro badge-Q17437796 badge-featuredarticle mw-list-item" title="featured article badge"><a href="https://ro.wikipedia.org/wiki/Sistemul_interna%C8%9Bional_de_unit%C4%83%C8%9Bi" title="Sistemul internațional de unități – Romanian" lang="ro" hreflang="ro" data-title="Sistemul internațional de unități" data-language-autonym="Română" data-language-local-name="Romanian" class="interlanguage-link-target">Română</a></li><li class="interlanguage-link interwiki-qu mw-list-item"><a href="https://qu.wikipedia.org/wiki/SI_tupuy" title="SI tupuy – Quechua" lang="qu" hreflang="qu" data-title="SI tupuy" data-language-autonym="Runa Simi" data-language-local-name="Quechua" class="interlanguage-link-target">Runa Simi</a></li><li class="interlanguage-link interwiki-rue mw-list-item"><a href="https://rue.wikipedia.org/wiki/%D0%A1%D0%B8%D1%81%D1%82%D0%B5%D0%BC%D0%B0_SI" title="Система SI – Rusyn" lang="rue" hreflang="rue" data-title="Система SI" data-language-autonym="Русиньскый" data-language-local-name="Rusyn" class="interlanguage-link-target">Русиньскый</a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/%D0%9C%D0%B5%D0%B6%D0%B4%D1%83%D0%BD%D0%B0%D1%80%D0%BE%D0%B4%D0%BD%D0%B0%D1%8F_%D1%81%D0%B8%D1%81%D1%82%D0%B5%D0%BC%D0%B0_%D0%B5%D0%B4%D0%B8%D0%BD%D0%B8%D1%86" title="Международная система единиц – Russian" lang="ru" hreflang="ru" data-title="Международная система единиц" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target">Русский</a></li><li class="interlanguage-link interwiki-sah mw-list-item"><a href="https://sah.wikipedia.org/wiki/%D0%9E%D0%BC%D1%83%D0%BA%D1%82%D0%B0%D1%80%D0%B4%D0%B0%D0%B0%D2%95%D1%8B_%D0%B1%D0%B8%D0%B8%D1%80%D0%B4%D0%B8%D0%BA_%D1%82%D1%83%D1%82%D1%83%D0%BC%D1%82%D0%B0%D1%82%D0%B0" title="Омуктардааҕы биирдик тутумтата – Yakut" lang="sah" hreflang="sah" data-title="Омуктардааҕы биирдик тутумтата" data-language-autonym="Саха тыла" data-language-local-name="Yakut" class="interlanguage-link-target">Саха тыла</a></li><li class="interlanguage-link interwiki-sc mw-list-item"><a href="https://sc.wikipedia.org/wiki/Sistema_Internatzionale_de_Unidades_de_Medida" title="Sistema Internatzionale de Unidades de Medida – Sardinian" lang="sc" hreflang="sc" data-title="Sistema Internatzionale de Unidades de Medida" data-language-autonym="Sardu" data-language-local-name="Sardinian" class="interlanguage-link-target">Sardu</a></li><li class="interlanguage-link interwiki-sco mw-list-item"><a href="https://sco.wikipedia.org/wiki/SI" title="SI – Scots" lang="sco" hreflang="sco" data-title="SI" data-language-autonym="Scots" data-language-local-name="Scots" class="interlanguage-link-target">Scots</a></li><li class="interlanguage-link interwiki-nso mw-list-item"><a href="https://nso.wikipedia.org/wiki/SI" title="SI – Northern Sotho" lang="nso" hreflang="nso" data-title="SI" data-language-autonym="Sesotho sa Leboa" data-language-local-name="Northern Sotho" class="interlanguage-link-target">Sesotho sa Leboa</a></li><li class="interlanguage-link interwiki-sq mw-list-item"><a href="https://sq.wikipedia.org/wiki/Sistemi_Nd%C3%ABrkomb%C3%ABtar_i_Nj%C3%ABsive" title="Sistemi Ndërkombëtar i Njësive – Albanian" lang="sq" hreflang="sq" data-title="Sistemi Ndërkombëtar i Njësive" data-language-autonym="Shqip" data-language-local-name="Albanian" class="interlanguage-link-target">Shqip</a></li><li class="interlanguage-link interwiki-scn mw-list-item"><a href="https://scn.wikipedia.org/wiki/Sistema_%27ntirnazziunali_di_unitati_di_misura" title="Sistema 'ntirnazziunali di unitati di misura – Sicilian" lang="scn" hreflang="scn" data-title="Sistema 'ntirnazziunali di unitati di misura" data-language-autonym="Sicilianu" data-language-local-name="Sicilian" class="interlanguage-link-target">Sicilianu</a></li><li class="interlanguage-link interwiki-si mw-list-item"><a href="https://si.wikipedia.org/wiki/%E0%B6%85%E0%B6%B1%E0%B7%8A%E0%B6%AD%E0%B6%BB%E0%B7%8A%E0%B6%A2%E0%B7%8F%E0%B6%AD%E0%B7%92%E0%B6%9A_%E0%B6%92%E0%B6%9A%E0%B6%9A_%E0%B6%B4%E0%B6%AF%E0%B7%8A%E0%B6%B0%E0%B6%AD%E0%B7%92%E0%B6%BA" title="අන්තර්ජාතික ඒකක පද්ධතිය – Sinhala" lang="si" hreflang="si" data-title="අන්තර්ජාතික ඒකක පද්ධතිය" data-language-autonym="සිංහල" data-language-local-name="Sinhala" class="interlanguage-link-target">සිංහල</a></li><li class="interlanguage-link interwiki-simple mw-list-item"><a href="https://simple.wikipedia.org/wiki/International_System_of_Units" title="International System of Units – Simple English" lang="en-simple" hreflang="en-simple" data-title="International System of Units" data-language-autonym="Simple English" data-language-local-name="Simple English" class="interlanguage-link-target">Simple English</a></li><li class="interlanguage-link interwiki-sd mw-list-item"><a href="https://sd.wikipedia.org/wiki/%D8%A7%DA%AA%D8%A7%D8%A6%D9%8A%D9%86_%D8%AC%D9%88_%D8%A8%D9%8A%D9%86_%D8%A7%D9%84%D8%A7%D9%82%D9%88%D8%A7%D9%85%D9%8A_%D9%86%D8%B8%D8%A7%D9%85" title="اڪائين جو بين الاقوامي نظام – Sindhi" lang="sd" hreflang="sd" data-title="اڪائين جو بين الاقوامي نظام" data-language-autonym="سنڌي" data-language-local-name="Sindhi" class="interlanguage-link-target">سنڌي</a></li><li class="interlanguage-link interwiki-sk mw-list-item"><a href="https://sk.wikipedia.org/wiki/SI" title="SI – Slovak" lang="sk" hreflang="sk" data-title="SI" data-language-autonym="Slovenčina" data-language-local-name="Slovak" class="interlanguage-link-target">Slovenčina</a></li><li class="interlanguage-link interwiki-sl mw-list-item"><a href="https://sl.wikipedia.org/wiki/Mednarodni_sistem_enot" title="Mednarodni sistem enot – Slovenian" lang="sl" hreflang="sl" data-title="Mednarodni sistem enot" data-language-autonym="Slovenščina" data-language-local-name="Slovenian" class="interlanguage-link-target">Slovenščina</a></li><li class="interlanguage-link interwiki-cu mw-list-item"><a href="https://cu.wikipedia.org/wiki/%D0%9C%D1%94%D0%B6%D0%B4%D0%BE%D1%83%D0%BD%D0%B0%D1%80%D0%BE%D0%B4%D1%8C%D0%BD%D1%8A_%D0%BC%D1%A3%D1%80%D1%8A_%D1%81%D1%B7%D1%81%D1%82%D0%B8%D0%BC%D0%B0" title="Мєждоународьнъ мѣръ сѷстима – Church Slavic" lang="cu" hreflang="cu" data-title="Мєждоународьнъ мѣръ сѷстима" data-language-autonym="Словѣньскъ / ⰔⰎⰑⰂⰡⰐⰠⰔⰍⰟ" data-language-local-name="Church Slavic" class="interlanguage-link-target">Словѣньскъ / ⰔⰎⰑⰂⰡⰐⰠⰔⰍⰟ</a></li><li class="interlanguage-link interwiki-so mw-list-item"><a href="https://so.wikipedia.org/wiki/Horgale_(Fiisikis)" title="Horgale (Fiisikis) – Somali" lang="so" hreflang="so" data-title="Horgale (Fiisikis)" data-language-autonym="Soomaaliga" data-language-local-name="Somali" class="interlanguage-link-target">Soomaaliga</a></li><li class="interlanguage-link interwiki-ckb mw-list-item"><a href="https://ckb.wikipedia.org/wiki/%D8%B3%DB%8C%D8%B3%D8%AA%D9%85%DB%8C_%D9%86%DB%8E%D9%88%D9%86%DB%95%D8%AA%DB%95%D9%88%DB%95%DB%8C%DB%8C%DB%8C_%DB%8C%DB%95%DA%A9%DB%95%DA%A9%D8%A7%D9%86" title="سیستمی نێونەتەوەییی یەکەکان – Central Kurdish" lang="ckb" hreflang="ckb" data-title="سیستمی نێونەتەوەییی یەکەکان" data-language-autonym="کوردی" data-language-local-name="Central Kurdish" class="interlanguage-link-target">کوردی</a></li><li class="interlanguage-link interwiki-sr mw-list-item"><a href="https://sr.wikipedia.org/wiki/%D0%9C%D0%B5%D1%92%D1%83%D0%BD%D0%B0%D1%80%D0%BE%D0%B4%D0%BD%D0%B8_%D1%81%D0%B8%D1%81%D1%82%D0%B5%D0%BC_%D1%98%D0%B5%D0%B4%D0%B8%D0%BD%D0%B8%D1%86%D0%B0" title="Међународни систем јединица – Serbian" lang="sr" hreflang="sr" data-title="Међународни систем јединица" data-language-autonym="Српски / srpski" data-language-local-name="Serbian" class="interlanguage-link-target">Српски / srpski</a></li><li class="interlanguage-link interwiki-sh mw-list-item"><a href="https://sh.wikipedia.org/wiki/Me%C4%91unarodni_sistem_%D1%98edinica" title="Međunarodni sistem јedinica – Serbo-Croatian" lang="sh" hreflang="sh" data-title="Međunarodni sistem јedinica" data-language-autonym="Srpskohrvatski / српскохрватски" data-language-local-name="Serbo-Croatian" class="interlanguage-link-target">Srpskohrvatski / српскохрватски</a></li><li class="interlanguage-link interwiki-su mw-list-item"><a href="https://su.wikipedia.org/wiki/Sistem_Hijian_Internasional" title="Sistem Hijian Internasional – Sundanese" lang="su" hreflang="su" data-title="Sistem Hijian Internasional" data-language-autonym="Sunda" data-language-local-name="Sundanese" class="interlanguage-link-target">Sunda</a></li><li class="interlanguage-link interwiki-fi mw-list-item"><a href="https://fi.wikipedia.org/wiki/Kansainv%C3%A4linen_yksikk%C3%B6j%C3%A4rjestelm%C3%A4" title="Kansainvälinen yksikköjärjestelmä – Finnish" lang="fi" hreflang="fi" data-title="Kansainvälinen yksikköjärjestelmä" data-language-autonym="Suomi" data-language-local-name="Finnish" class="interlanguage-link-target">Suomi</a></li><li class="interlanguage-link interwiki-sv mw-list-item"><a href="https://sv.wikipedia.org/wiki/Internationella_m%C3%A5ttenhetssystemet" title="Internationella måttenhetssystemet – Swedish" lang="sv" hreflang="sv" data-title="Internationella måttenhetssystemet" data-language-autonym="Svenska" data-language-local-name="Swedish" class="interlanguage-link-target">Svenska</a></li><li class="interlanguage-link interwiki-tl mw-list-item"><a href="https://tl.wikipedia.org/wiki/Pandaigdigang_Sistema_ng_mga_Yunit" title="Pandaigdigang Sistema ng mga Yunit – Tagalog" lang="tl" hreflang="tl" data-title="Pandaigdigang Sistema ng mga Yunit" data-language-autonym="Tagalog" data-language-local-name="Tagalog" class="interlanguage-link-target">Tagalog</a></li><li class="interlanguage-link interwiki-ta mw-list-item"><a href="https://ta.wikipedia.org/wiki/%E0%AE%85%E0%AE%A9%E0%AF%88%E0%AE%A4%E0%AF%8D%E0%AE%A4%E0%AF%81%E0%AE%B2%E0%AE%95_%E0%AE%AE%E0%AF%81%E0%AE%B1%E0%AF%88_%E0%AE%85%E0%AE%B2%E0%AE%95%E0%AF%81%E0%AE%95%E0%AE%B3%E0%AF%8D" title="அனைத்துலக முறை அலகுகள் – Tamil" lang="ta" hreflang="ta" data-title="அனைத்துலக முறை அலகுகள்" data-language-autonym="தமிழ்" data-language-local-name="Tamil" class="interlanguage-link-target">தமிழ்</a></li><li class="interlanguage-link interwiki-kab mw-list-item"><a href="https://kab.wikipedia.org/wiki/Anagraw_agra%C9%A3lan_n_tiynin" title="Anagraw agraɣlan n tiynin – Kabyle" lang="kab" hreflang="kab" data-title="Anagraw agraɣlan n tiynin" data-language-autonym="Taqbaylit" data-language-local-name="Kabyle" class="interlanguage-link-target">Taqbaylit</a></li><li class="interlanguage-link interwiki-roa-tara mw-list-item"><a href="https://roa-tara.wikipedia.org/wiki/Sisteme_%27Ndernazionale_de_aunit%C3%A0_de_mesure" title="Sisteme 'Ndernazionale de aunità de mesure – Tarantino" lang="nap-x-tara" hreflang="nap-x-tara" data-title="Sisteme 'Ndernazionale de aunità de mesure" data-language-autonym="Tarandíne" data-language-local-name="Tarantino" class="interlanguage-link-target">Tarandíne</a></li><li class="interlanguage-link interwiki-tt badge-Q17437798 badge-goodarticle mw-list-item" title="good article badge"><a href="https://tt.wikipedia.org/wiki/%D0%A5%D0%B0%D0%BB%D1%8B%D0%BA%D0%B0%D1%80%D0%B0_%D0%B1%D0%B5%D1%80%D3%99%D0%BC%D0%BB%D0%B5%D0%BA%D0%BB%D3%99%D1%80_%D1%81%D0%B8%D1%81%D1%82%D0%B5%D0%BC%D0%B0%D1%81%D1%8B" title="Халыкара берәмлекләр системасы – Tatar" lang="tt" hreflang="tt" data-title="Халыкара берәмлекләр системасы" data-language-autonym="Татарча / tatarça" data-language-local-name="Tatar" class="interlanguage-link-target">Татарча / tatarça</a></li><li class="interlanguage-link interwiki-te mw-list-item"><a href="https://te.wikipedia.org/wiki/%E0%B0%85%E0%B0%82%E0%B0%A4%E0%B0%B0%E0%B1%8D%E0%B0%9C%E0%B0%BE%E0%B0%A4%E0%B1%80%E0%B0%AF_%E0%B0%AA%E0%B1%8D%E0%B0%B0%E0%B0%AE%E0%B0%BE%E0%B0%A3%E0%B0%BE%E0%B0%B2_%E0%B0%AA%E0%B0%A6%E0%B1%8D%E0%B0%A7%E0%B0%A4%E0%B0%BF" title="అంతర్జాతీయ ప్రమాణాల పద్ధతి – Telugu" lang="te" hreflang="te" data-title="అంతర్జాతీయ ప్రమాణాల పద్ధతి" data-language-autonym="తెలుగు" data-language-local-name="Telugu" class="interlanguage-link-target">తెలుగు</a></li><li class="interlanguage-link interwiki-th mw-list-item"><a href="https://th.wikipedia.org/wiki/%E0%B8%A3%E0%B8%B0%E0%B8%9A%E0%B8%9A%E0%B8%AB%E0%B8%99%E0%B9%88%E0%B8%A7%E0%B8%A2%E0%B8%A7%E0%B8%B1%E0%B8%94%E0%B8%A3%E0%B8%B0%E0%B8%AB%E0%B8%A7%E0%B9%88%E0%B8%B2%E0%B8%87%E0%B8%9B%E0%B8%A3%E0%B8%B0%E0%B9%80%E0%B8%97%E0%B8%A8" title="ระบบหน่วยวัดระหว่างประเทศ – Thai" lang="th" hreflang="th" data-title="ระบบหน่วยวัดระหว่างประเทศ" data-language-autonym="ไทย" data-language-local-name="Thai" class="interlanguage-link-target">ไทย</a></li><li class="interlanguage-link interwiki-ti mw-list-item"><a href="https://ti.wikipedia.org/wiki/%E1%8B%93%E1%88%88%E1%88%9D%E1%88%88%E1%8A%BB%E1%8B%8A_%E1%88%B5%E1%88%AD%E1%8B%93%E1%89%B5_%E1%8A%A3%E1%88%83%E1%8B%B1%E1%89%B3%E1%89%B5_%E1%88%98%E1%88%88%E1%8A%AD%E1%8B%92" title="ዓለምለኻዊ ስርዓት ኣሃዱታት መለክዒ – Tigrinya" lang="ti" hreflang="ti" data-title="ዓለምለኻዊ ስርዓት ኣሃዱታት መለክዒ" data-language-autonym="ትግርኛ" data-language-local-name="Tigrinya" class="interlanguage-link-target">ትግርኛ</a></li><li class="interlanguage-link interwiki-tr mw-list-item"><a href="https://tr.wikipedia.org/wiki/Uluslararas%C4%B1_Birimler_Sistemi" title="Uluslararası Birimler Sistemi – Turkish" lang="tr" hreflang="tr" data-title="Uluslararası Birimler Sistemi" data-language-autonym="Türkçe" data-language-local-name="Turkish" class="interlanguage-link-target">Türkçe</a></li><li class="interlanguage-link interwiki-kcg mw-list-item"><a href="https://kcg.wikipedia.org/wiki/Si%CC%B1tem_Mai-nkyang_Bibyin_Swanta" title="Si̱tem Mai-nkyang Bibyin Swanta – Tyap" lang="kcg" hreflang="kcg" data-title="Si̱tem Mai-nkyang Bibyin Swanta" data-language-autonym="Tyap" data-language-local-name="Tyap" class="interlanguage-link-target">Tyap</a></li><li class="interlanguage-link interwiki-tyv mw-list-item"><a href="https://tyv.wikipedia.org/wiki/%D0%98%D0%BD%D1%82%D0%B5%D1%80%D0%BD%D0%B0%D1%86%D0%B8%D0%BE%D0%BD%D0%B0%D0%BB%D0%B4%D1%8B%D0%B3_%D1%85%D0%B5%D0%BC%D1%87%D0%B5%D0%B3%D0%BB%D0%B5%D1%80_%D1%81%D0%B8%D1%81%D1%82%D0%B5%D0%BC%D0%B0%D0%B7%D1%8B" title="Интернационалдыг хемчеглер системазы – Tuvinian" lang="tyv" hreflang="tyv" data-title="Интернационалдыг хемчеглер системазы" data-language-autonym="Тыва дыл" data-language-local-name="Tuvinian" class="interlanguage-link-target">Тыва дыл</a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a 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<div class="mw-indicators"> </div> <div id="siteSub" class="noprint">From Wikipedia, the free encyclopedia</div> </div> <div id="contentSub"><div id="mw-content-subtitle"></div></div> <div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Modern form of the metric system</div> <style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">"SI" redirects here. For the chemical element with symbol Si, see <a href="/wiki/Silicon" title="Silicon">Silicon</a>. For other uses, see <a href="/wiki/SI_(disambiguation)" class="mw-redirect mw-disambig" title="SI (disambiguation)">SI (disambiguation)</a>.</div> The International System of Units, internationally known by the abbreviation SI (from French Système international d'unités), is the modern form of the <a href="/wiki/Metric_system" title="Metric system">metric system</a> and the world's most widely used <a href="/wiki/System_of_measurement" class="mw-redirect" title="System of measurement">system of measurement</a>. Coordinated by the <a href="/wiki/International_Bureau_of_Weights_and_Measures" title="International Bureau of Weights and Measures">International Bureau of Weights and Measures</a> (abbreviated BIPM from <a href="/wiki/French_language" title="French language">French</a>: Bureau international des poids et mesures) it is the only system of measurement with official status in nearly every country in the world, employed in science, technology, industry, and everyday commerce. <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:SI_Illustration_Base_Units_and_Constants_Colour_Full.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/3/3c/SI_Illustration_Base_Units_and_Constants_Colour_Full.svg/220px-SI_Illustration_Base_Units_and_Constants_Colour_Full.svg.png" decoding="async" width="220" height="220" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/3/3c/SI_Illustration_Base_Units_and_Constants_Colour_Full.svg/330px-SI_Illustration_Base_Units_and_Constants_Colour_Full.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/3/3c/SI_Illustration_Base_Units_and_Constants_Colour_Full.svg/440px-SI_Illustration_Base_Units_and_Constants_Colour_Full.svg.png 2x" data-file-width="512" data-file-height="512" /></a><figcaption>SI <a href="#SI_base_units">base units</a> (outer ring) and <a href="#SI_defining_constants">constants</a> (inner ring) </figcaption></figure> <table class="wikitable floatright" style="width: 400px; text-align:center;"> <caption>The seven SI base units </caption> <tbody><tr> <th scope="col">Symbol </th> <th scope="col">Name </th> <th scope="col">Quantity </th></tr> <tr> <th scope="row">s </th> <td><a href="/wiki/Second" title="Second">second</a></td> <td><a href="/wiki/Time" title="Time">time</a> </td></tr> <tr> <th scope="row">m </th> <td><a href="/wiki/Metre" title="Metre">metre</a></td> <td><a href="/wiki/Length" title="Length">length</a> </td></tr> <tr> <th scope="row">kg </th> <td><a href="/wiki/Kilogram" title="Kilogram">kilogram</a></td> <td><a href="/wiki/Mass" title="Mass">mass</a> </td></tr> <tr> <th scope="row">A </th> <td><a href="/wiki/Ampere" title="Ampere">ampere</a></td> <td><a href="/wiki/Electric_current" title="Electric current">electric current</a> </td></tr> <tr> <th scope="row">K </th> <td><a href="/wiki/Kelvin" title="Kelvin">kelvin</a></td> <td><a href="/wiki/Thermodynamic_temperature" title="Thermodynamic temperature">thermodynamic temperature</a> </td></tr> <tr> <th scope="row">mol </th> <td><a href="/wiki/Mole_(unit)" title="Mole (unit)">mole</a></td> <td><a href="/wiki/Amount_of_substance" title="Amount of substance">amount of substance</a> </td></tr> <tr> <th scope="row">cd </th> <td><a href="/wiki/Candela" title="Candela">candela</a></td> <td><a href="/wiki/Luminous_intensity" title="Luminous intensity">luminous intensity</a> </td></tr></tbody></table> The SI comprises a <a href="/wiki/Coherence_(units_of_measurement)" title="Coherence (units of measurement)">coherent</a> system of <a href="/wiki/Units_of_measurement" class="mw-redirect" title="Units of measurement">units of measurement</a> starting with seven <a href="/wiki/SI_base_unit" title="SI base unit">base units</a>, which are the <a href="/wiki/Second" title="Second">second</a> (symbol s, the unit of <a href="/wiki/Time" title="Time">time</a>), <a href="/wiki/Metre" title="Metre">metre</a> (m, <a href="/wiki/Length" title="Length">length</a>), <a href="/wiki/Kilogram" title="Kilogram">kilogram</a> (kg, <a href="/wiki/Mass" title="Mass">mass</a>), <a href="/wiki/Ampere" title="Ampere">ampere</a> (A, <a href="/wiki/Electric_current" title="Electric current">electric current</a>), <a href="/wiki/Kelvin" title="Kelvin">kelvin</a> (K, <a href="/wiki/Thermodynamic_temperature" title="Thermodynamic temperature">thermodynamic temperature</a>), <a href="/wiki/Mole_(unit)" title="Mole (unit)">mole</a> (mol, <a href="/wiki/Amount_of_substance" title="Amount of substance">amount of substance</a>), and <a href="/wiki/Candela" title="Candela">candela</a> (cd, <a href="/wiki/Luminous_intensity" title="Luminous intensity">luminous intensity</a>). The system can accommodate coherent units for an unlimited number of additional quantities. These are called coherent <a href="/wiki/SI_derived_unit" title="SI derived unit">derived units</a>, which can always be represented as products of powers of the base units. Twenty-two coherent derived units have been provided with special names and symbols. The seven base units and the 22 coherent derived units with special names and symbols may be used in combination to express other coherent derived units. Since the sizes of coherent units will be convenient for only some applications and not for others, the SI provides twenty-four <a href="/wiki/Metric_prefix" title="Metric prefix">prefixes</a> which, when added to the name and symbol of a coherent unit produce twenty-four additional (non-coherent) SI units for the same quantity; these non-coherent units are always decimal (i.e. power-of-ten) multiples and sub-multiples of the coherent unit. The current way of defining the SI is a result of a decades-long move towards increasingly abstract and idealised formulation in which the <a href="/wiki/Realisation_(metrology)" title="Realisation (metrology)">realisations</a> of the units are separated conceptually from the definitions. A consequence is that as science and technologies develop, new and superior realisations may be introduced without the need to redefine the unit. One problem with artefacts is that they can be lost, damaged, or changed; another is that they introduce uncertainties that cannot be reduced by advancements in science and technology. The original motivation for the development of the SI was the diversity of units that had sprung up within the <a href="/wiki/Centimetre%E2%80%93gram%E2%80%93second_system_of_units" title="Centimetre–gram–second system of units">centimetre–gram–second</a> (CGS) systems (specifically the inconsistency between the systems of <a href="/wiki/Electrostatic_units" class="mw-redirect" title="Electrostatic units">electrostatic units</a> and <a href="/wiki/Electromagnetic_units" class="mw-redirect" title="Electromagnetic units">electromagnetic units</a>) and the lack of coordination between the various <a href="/wiki/Discipline_(academia)" class="mw-redirect" title="Discipline (academia)">disciplines</a> that used them. The General Conference on Weights and Measures (French: Conférence générale des poids et mesures – CGPM), which was established by the <a href="/wiki/Metre_Convention" title="Metre Convention">Metre Convention</a> of 1875, brought together many international organisations to establish the definitions and standards of a new system and to standardise the rules for writing and presenting measurements. The system was published in 1960 as a result of an initiative that began in 1948, and is based on the <a href="/wiki/MKS_system_of_units" class="mw-redirect" title="MKS system of units">metre–kilogram–second system of units</a> (MKS) combined with ideas from the development of the CGS system. <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Definition">Definition</h2>[<a href="/w/index.php?title=International_System_of_Units&action=edit&section=1" title="Edit section: Definition">edit</a>]</div> The International System of Units consists of a set of defining constants with corresponding base units, derived units, and a set of decimal-based multipliers that are used as prefixes.<a href="#cite_note-SIBrochure9thEd-1">[1]</a>: 125  <div class="mw-heading mw-heading3"><h3 id="SI_defining_constants">SI defining constants</h3>[<a href="/w/index.php?title=International_System_of_Units&action=edit&section=2" title="Edit section: SI defining constants">edit</a>]</div> <table class="wikitable floatright" style="width: 400px; text-align:center;"> <caption>SI defining constants </caption> <tbody><tr> <th scope="col">Symbol </th> <th scope="col">Defining constant </th> <th scope="col">Exact value </th></tr> <tr> <th scope="row">ΔνCs </th> <td><a href="/wiki/Caesium_standard" title="Caesium standard">hyperfine transition frequency of Cs</a></td> <td>9192631770 Hz </td></tr> <tr> <th scope="row">c </th> <td><a href="/wiki/Speed_of_light" title="Speed of light">speed of light</a></td> <td>299792458 m/s </td></tr> <tr> <th scope="row">h </th> <td><a href="/wiki/Planck_constant" title="Planck constant">Planck constant</a></td> <td>6.62607015×10−34 J⋅s </td></tr> <tr> <th scope="row">e </th> <td><a href="/wiki/Elementary_charge" title="Elementary charge">elementary charge</a></td> <td>1.602176634×10−19 C </td></tr> <tr> <th scope="row">k </th> <td><a href="/wiki/Boltzmann_constant" title="Boltzmann constant">Boltzmann constant</a></td> <td>1.380649×10−23 J/K </td></tr> <tr> <th scope="row">NA </th> <td><a href="/wiki/Avogadro_constant" title="Avogadro constant">Avogadro constant</a></td> <td>6.02214076×1023 mol−1 </td></tr> <tr> <th scope="row">Kcd </th> <td><a href="/wiki/Luminous_efficacy" title="Luminous efficacy">luminous efficacy</a> of 540 THz radiation</td> <td>683 lm/W </td></tr></tbody></table> The seven defining constants are the most fundamental feature of the definition of the system of units.<a href="#cite_note-SIBrochure9thEd-1">[1]</a>: 125  The magnitudes of all SI units are defined by declaring that seven constants have certain exact numerical values when expressed in terms of their SI units. These defining constants are the <a href="/wiki/Speed_of_light" title="Speed of light">speed of light</a> in vacuum c, the <a href="/wiki/Caesium_standard" title="Caesium standard">hyperfine transition frequency of caesium</a> ΔνCs, the <a href="/wiki/Planck_constant" title="Planck constant">Planck constant</a> h, the <a href="/wiki/Elementary_charge" title="Elementary charge">elementary charge</a> e, the <a href="/wiki/Boltzmann_constant" title="Boltzmann constant">Boltzmann constant</a> k, the <a href="/wiki/Avogadro_constant" title="Avogadro constant">Avogadro constant</a> NA, and the <a href="/wiki/Luminous_efficacy" title="Luminous efficacy">luminous efficacy</a> Kcd. The nature of the defining constants ranges from fundamental constants of nature such as c to the purely technical constant Kcd. The values assigned to these constants were fixed to ensure continuity with previous definitions of the base units.<a href="#cite_note-SIBrochure9thEd-1">[1]</a>: 128  <div class="mw-heading mw-heading3"><h3 id="SI_base_units">SI base units</h3>[<a href="/w/index.php?title=International_System_of_Units&action=edit&section=3" title="Edit section: SI base units">edit</a>]</div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/SI_base_unit" title="SI base unit">SI base unit</a></div> The SI selects seven units to serve as <a href="/wiki/SI_base_unit" title="SI base unit">base units</a>, corresponding to seven base physical quantities. They are the <a href="/wiki/Second" title="Second">second</a>, with the symbol s, which is the SI unit of the physical quantity of <a href="/wiki/Time" title="Time">time</a>; the <a href="/wiki/Metre" title="Metre">metre</a>, symbol m, the SI unit of <a href="/wiki/Length" title="Length">length</a>; <a href="/wiki/Kilogram" title="Kilogram">kilogram</a> (kg, the unit of <a href="/wiki/Mass" title="Mass">mass</a>); <a href="/wiki/Ampere" title="Ampere">ampere</a> (A, <a href="/wiki/Electric_current" title="Electric current">electric current</a>); <a href="/wiki/Kelvin" title="Kelvin">kelvin</a> (K, <a href="/wiki/Thermodynamic_temperature" title="Thermodynamic temperature">thermodynamic temperature</a>); <a href="/wiki/Mole_(unit)" title="Mole (unit)">mole</a> (mol, <a href="/wiki/Amount_of_substance" title="Amount of substance">amount of substance</a>); and <a href="/wiki/Candela" title="Candela">candela</a> (cd, <a href="/wiki/Luminous_intensity" title="Luminous intensity">luminous intensity</a>).<a href="#cite_note-SIBrochure9thEd-1">[1]</a> The base units are defined in terms of the defining constants. For example, the kilogram is defined by taking the Planck constant h to be 6.62607015×10−34 J⋅s, giving the expression in terms of the defining constants<a href="#cite_note-SIBrochure9thEd-1">[1]</a>: 131  <dl><dd>1 kg = <style data-mw-deduplicate="TemplateStyles:r1214402035">.mw-parser-output .sfrac{white-space:nowrap}.mw-parser-output .sfrac.tion,.mw-parser-output .sfrac .tion{display:inline-block;vertical-align:-0.5em;font-size:85%;text-align:center}.mw-parser-output .sfrac .num{display:block;line-height:1em;margin:0.0em 0.1em;border-bottom:1px solid}.mw-parser-output .sfrac .den{display:block;line-height:1em;margin:0.1em 0.1em}.mw-parser-output .sr-only{border:0;clip:rect(0,0,0,0);clip-path:polygon(0px 0px,0px 0px,0px 0px);height:1px;margin:-1px;overflow:hidden;padding:0;position:absolute;width:1px}</style>⁠(299792458)2/(6.62607015×10−34)(9192631770)⁠<link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035">⁠h ΔνCs/c2⁠.</dd></dl> All units in the SI can be expressed in terms of the base units, and the base units serve as a preferred set for expressing or analysing the relationships between units. The choice of which and even how many quantities to use as base quantities is not fundamental or even unique – it is a matter of convention.<a href="#cite_note-SIBrochure9thEd-1">[1]</a>: <span title="Page: 126
Quotation: "... the choice of the base units was never unique, but grew historically and became familiar to users of the SI"" class="tooltip tooltip-dashed" style="border-bottom: 1px dashed;">126  <table class="wikitable" style="margin:1em auto 1em auto"> <caption><big>SI base units</big><a href="#cite_note-SIBrochure9thEd-1">[1]</a>: 136  </caption> <tbody><tr> <th scope="col">Unit name </th> <th scope="col">Unit symbol </th> <th scope="col"><a href="/wiki/Dimensional_analysis#Definition" title="Dimensional analysis">Dimension symbol</a> </th> <th scope="col"><a href="/wiki/Physical_quantity" title="Physical quantity">Quantity name</a> </th> <th scope="col" width="80">Typical symbols </th> <th scope="col">Definition </th></tr> <tr> <th scope="row"><a href="/wiki/Second" title="Second">second</a> </th> <td style="text-align:center">s </td> <td style="text-align:center"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\mathsf {T}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="sans-serif">T</mi> </mrow> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\mathsf {T}}}</annotation> </semantics> </math><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7860e4d66c67ce669b88f07a796b143537193daf" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.583ex; height:2.176ex;" alt="{\displaystyle {\mathsf {T}}}"> </td> <td><a href="/wiki/Time" title="Time">time</a> </td> <td><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle t}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>t</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle t}</annotation> </semantics> </math><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/65658b7b223af9e1acc877d848888ecdb4466560" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:0.84ex; height:2.009ex;" alt="{\displaystyle t}"> </td> <td>The duration of 9192631770 periods of the radiation corresponding to the transition between the two <a href="/wiki/Hyperfine_structure" title="Hyperfine structure">hyperfine</a> levels of the <a href="/wiki/Ground_state" title="Ground state">ground state</a> of the <a href="/wiki/Caesium-133" class="mw-redirect" title="Caesium-133">caesium-133</a> atom. </td></tr> <tr> <th scope="row"><a href="/wiki/Metre" title="Metre">metre</a> </th> <td style="text-align:center">m </td> <td style="text-align:center"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\mathsf {L}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="sans-serif">L</mi> </mrow> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\mathsf {L}}}</annotation> </semantics> </math><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/4d25704a85c37e68d78dd9f549587912bf314b3c" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.26ex; height:2.176ex;" alt="{\displaystyle {\mathsf {L}}}"> </td> <td><a href="/wiki/Length" title="Length">length</a> </td> <td><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle l}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>l</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle l}</annotation> </semantics> </math><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/829091f745070b9eb97a80244129025440a1cfac" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:0.693ex; height:2.176ex;" alt="{\displaystyle l}">, <math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle x}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>x</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle x}</annotation> </semantics> </math><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/87f9e315fd7e2ba406057a97300593c4802b53e4" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.33ex; height:1.676ex;" alt="{\displaystyle x}">, <math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle r}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>r</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle r}</annotation> </semantics> </math><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/0d1ecb613aa2984f0576f70f86650b7c2a132538" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.049ex; height:1.676ex;" alt="{\displaystyle r}">, etc. </td> <td>The distance travelled by light in vacuum in <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035">⁠1/299792458⁠ second. </td></tr> <tr> <th scope="row"><a href="/wiki/Kilogram" title="Kilogram">kilogram</a> <a href="#cite_note-2">[n 1]</a> </th> <td style="text-align:center">kg </td> <td style="text-align:center"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\mathsf {M}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="sans-serif">M</mi> </mrow> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\mathsf {M}}}</annotation> </semantics> </math><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/8d2825874b1ad46c9fab585139f2f5e6e6b3b200" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:2.033ex; height:2.176ex;" alt="{\displaystyle {\mathsf {M}}}"> </td> <td><a href="/wiki/Mass" title="Mass">mass</a> </td> <td><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle m}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>m</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle m}</annotation> </semantics> </math><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/0a07d98bb302f3856cbabc47b2b9016692e3f7bc" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:2.04ex; height:1.676ex;" alt="{\displaystyle m}"> </td> <td>The kilogram is defined by setting the <a href="/wiki/Planck_constant" title="Planck constant">Planck constant</a> h to 6.62607015×10−34 J⋅s (J = kg⋅m2⋅s−2), given the definitions of the metre and the second.<a href="#cite_note-NIST_2018-11-3">[2]</a> </td></tr> <tr> <th scope="row"><a href="/wiki/Ampere" title="Ampere">ampere</a> </th> <td style="text-align:center">A </td> <td style="text-align:center"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\mathsf {I}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="sans-serif">I</mi> </mrow> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\mathsf {I}}}</annotation> </semantics> </math><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/878f98bf0bd7d51626d3e31ac531de48f5092654" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:0.647ex; height:2.176ex;" alt="{\displaystyle {\mathsf {I}}}"> </td> <td><a href="/wiki/Electric_current" title="Electric current">electric current</a> </td> <td><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle I,\;i}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>I</mi> <mo>,</mo> <mspace width="thickmathspace" /> <mi>i</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle I,\;i}</annotation> </semantics> </math><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/1522ecdc2a53d061ebc61cb456ed7d0ad8cfc554" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:3.653ex; height:2.509ex;" alt="{\displaystyle I,\;i}"> </td> <td>The flow of <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035">⁠1/1.602176634×10−19⁠ times the <a href="/wiki/Elementary_charge" title="Elementary charge">elementary charge</a> e per second, which is approximately 6.2415090744×1018 elementary charges per second. </td></tr> <tr> <th scope="row"><a href="/wiki/Kelvin" title="Kelvin">kelvin</a> </th> <td style="text-align:center">K </td> <td style="text-align:center"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\mathsf {\Theta }}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="sans-serif">Θ</mi> </mrow> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\mathsf {\Theta }}}</annotation> </semantics> </math><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/6a6843373458fc7f6209bc5190f8759ab9d28ce3" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.808ex; height:2.176ex;" alt="{\displaystyle {\mathsf {\Theta }}}"> </td> <td><a href="/wiki/Thermodynamic_temperature" title="Thermodynamic temperature">thermodynamic temperature</a> </td> <td><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle T}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>T</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle T}</annotation> </semantics> </math><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/ec7200acd984a1d3a3d7dc455e262fbe54f7f6e0" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.636ex; height:2.176ex;" alt="{\displaystyle T}"> </td> <td>The kelvin is defined by setting the fixed numerical value of the <a href="/wiki/Boltzmann_constant" title="Boltzmann constant">Boltzmann constant</a> k to 1.380649×10−23 J⋅K−1, (J = kg⋅m2⋅s−2), given the definition of the kilogram, the metre, and the second. </td></tr> <tr> <th scope="row"><a href="/wiki/Mole_(unit)" title="Mole (unit)">mole</a> </th> <td style="text-align:center">mol </td> <td style="text-align:center"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\mathsf {N}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="sans-serif">N</mi> </mrow> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\mathsf {N}}}</annotation> </semantics> </math><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/0ffa685ddb7886a1992609db0700aebc0990e611" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.646ex; height:2.176ex;" alt="{\displaystyle {\mathsf {N}}}"> </td> <td><a href="/wiki/Amount_of_substance" title="Amount of substance">amount of substance</a> </td> <td><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle n}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>n</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle n}</annotation> </semantics> </math><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/a601995d55609f2d9f5e233e36fbe9ea26011b3b" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.395ex; height:1.676ex;" alt="{\displaystyle n}"> </td> <td>The amount of substance of 6.02214076×1023 elementary entities.<a href="#cite_note-4">[n 2]</a> This number is the fixed numerical value of the <a href="/wiki/Avogadro_constant" title="Avogadro constant">Avogadro constant</a>, NA, when expressed in the unit mol−1. </td></tr> <tr> <th scope="row"><a href="/wiki/Candela" title="Candela">candela</a> </th> <td style="text-align:center">cd </td> <td style="text-align:center"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\mathsf {J}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="sans-serif">J</mi> </mrow> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\mathsf {J}}}</annotation> </semantics> </math><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/a3921f53f831b8865be77debe5b3f1f55a9bd06a" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.097ex; height:2.176ex;" alt="{\displaystyle {\mathsf {J}}}"> </td> <td><a href="/wiki/Luminous_intensity" title="Luminous intensity">luminous intensity</a> </td> <td><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle I_{\rm {v}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>I</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">v</mi> </mrow> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle I_{\rm {v}}}</annotation> </semantics> </math><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/5b38ff9fb480c0549cdb6480df214e4c0df39ae7" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.123ex; height:2.509ex;" alt="{\displaystyle I_{\rm {v}}}"> </td> <td>The luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 5.4×1014 hertz and that has a radiant intensity in that direction of <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035">⁠1/683⁠ watt per <a href="/wiki/Steradian" title="Steradian">steradian</a>. </td></tr> <tr> <td colspan="6"> <dl><dt>Notes</dt></dl> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap"><ol class="references"> <li id="cite_note-2"><a href="#cite_ref-2">^</a> Despite the prefix "kilo-", the kilogram is the coherent base unit of mass, and is used in the definitions of derived units. Nonetheless, prefixes for the unit of mass are determined as if the gram were the base unit. </li> <li id="cite_note-4"><a href="#cite_ref-4">^</a> When the mole is used, the elementary entities must be specified and may be <a href="/wiki/Atom" title="Atom">atoms</a>, <a href="/wiki/Molecule" title="Molecule">molecules</a>, <a href="/wiki/Ion" title="Ion">ions</a>, <a href="/wiki/Electron" title="Electron">electrons</a>, other particles, or specified groups of such particles. </li> </ol></div></div> </td></tr></tbody></table> <div class="mw-heading mw-heading3"><h3 id="Derived_units">Derived units</h3>[<a href="/w/index.php?title=International_System_of_Units&action=edit&section=4" title="Edit section: Derived units">edit</a>]</div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/SI_derived_unit" title="SI derived unit">SI derived unit</a></div> The system allows for an unlimited number of additional units, called <a href="/wiki/SI_derived_unit" title="SI derived unit">derived units</a>, which can always be represented as products of powers of the base units, possibly with a nontrivial numeric multiplier. When that multiplier is one, the unit is called a <a href="/wiki/Coherence_(units_of_measurement)" title="Coherence (units of measurement)">coherent</a> derived unit. For example, the coherent derived SI unit of <a href="/wiki/Velocity" title="Velocity">velocity</a> is the <a href="/wiki/Metre_per_second" title="Metre per second">metre per second</a>, with the symbol m/s.<a href="#cite_note-SIBrochure9thEd-1">[1]</a>: 139  The base and coherent derived units of the SI together form a coherent system of units (the set of coherent SI units). A useful property of a coherent system is that when the numerical values of physical quantities are expressed in terms of the units of the system, then the equations between the numerical values have exactly the same form, including numerical factors, as the corresponding equations between the physical quantities.<a href="#cite_note-ISO80000-1-5">[3]</a>: 6  Twenty-two coherent derived units have been provided with special names and symbols as shown in the table below. The radian and steradian have no base units but are treated as derived units for historical reasons.<a href="#cite_note-SIBrochure9thEd-1">[1]</a>: 137  <table class="wikitable floatleft" style="margin:1em auto 1em auto;line-height:1.4"> <caption><big>The 22 SI derived units with special names and symbols</big><a href="#cite_note-NIST330-6">[4]</a>: 15  </caption> <tbody><tr> <th scope="col">Name </th> <th scope="col">Symbol </th> <th scope="col">Quantity </th> <th scope="col">In SI base units </th> <th scope="col">In other SI units </th></tr> <tr> <th scope="row"><a href="/wiki/Radian" title="Radian">radian</a><a href="#cite_note-:0-7">[N 1]</a> </th> <td style="text-align:center;">rad </td> <td><a href="/wiki/Angle" title="Angle">plane angle</a> </td> <td style="text-align:center;">m/m </td> <td style="text-align:center;">1 </td></tr> <tr> <th scope="row"><a href="/wiki/Steradian" title="Steradian">steradian</a><a href="#cite_note-:0-7">[N 1]</a> </th> <td style="text-align:center;">sr </td> <td><a href="/wiki/Solid_angle" title="Solid angle">solid angle</a> </td> <td style="text-align:center;">m2/m2 </td> <td style="text-align:center;">1 </td></tr> <tr> <th scope="row"><a href="/wiki/Hertz" title="Hertz">hertz</a> </th> <td style="text-align:center;">Hz </td> <td><a href="/wiki/Frequency" title="Frequency">frequency</a> </td> <td style="text-align:center;">s−1 </td> <td> </td></tr> <tr> <th scope="row"><a href="/wiki/Newton_(unit)" title="Newton (unit)">newton</a> </th> <td style="text-align:center;">N </td> <td><a href="/wiki/Force" title="Force">force</a> </td> <td style="text-align:center;">kg⋅m⋅s−2 </td> <td> </td></tr> <tr> <th scope="row"><a href="/wiki/Pascal_(unit)" title="Pascal (unit)">pascal</a> </th> <td style="text-align:center;">Pa </td> <td><a href="/wiki/Pressure" title="Pressure">pressure</a>, <a href="/wiki/Stress_(physics)" class="mw-redirect" title="Stress (physics)">stress</a> </td> <td style="text-align:center;">kg⋅m−1⋅s−2 </td> <td style="text-align:center;">N/m2 = J/m3 </td></tr> <tr> <th scope="row"><a href="/wiki/Joule" title="Joule">joule</a> </th> <td style="text-align:center;">J </td> <td><a href="/wiki/Energy" title="Energy">energy</a>, <a href="/wiki/Mechanical_work" class="mw-redirect" title="Mechanical work">work</a>, amount of <a href="/wiki/Heat" title="Heat">heat</a> </td> <td style="text-align:center;">kg⋅m2⋅s−2 </td> <td style="text-align:center;">N⋅m = Pa⋅m3 </td></tr> <tr> <th scope="row"><a href="/wiki/Watt" title="Watt">watt</a> </th> <td style="text-align:center;">W </td> <td><a href="/wiki/Power_(physics)" title="Power (physics)">power</a>, <a href="/wiki/Radiant_flux" title="Radiant flux">radiant flux</a> </td> <td style="text-align:center;">kg⋅m2⋅s−3 </td> <td style="text-align:center;">J/s </td></tr> <tr> <th scope="row"><a href="/wiki/Coulomb" title="Coulomb">coulomb</a> </th> <td style="text-align:center;">C </td> <td><a href="/wiki/Electric_charge" title="Electric charge">electric charge</a> </td> <td style="text-align:center;">s⋅A </td> <td> </td></tr> <tr> <th scope="row"><a href="/wiki/Volt" title="Volt">volt</a> </th> <td style="text-align:center;">V </td> <td><a href="/wiki/Electric_potential" title="Electric potential">electric potential</a>, (<a href="/wiki/Voltage" title="Voltage">voltage</a> in US; electric tension) </td> <td style="text-align:center;">kg⋅m2⋅s−3⋅A−1 </td> <td style="text-align:center;">W/A = J/C </td></tr> <tr> <th scope="row"><a href="/wiki/Farad" title="Farad">farad</a> </th> <td style="text-align:center;">F </td> <td><a href="/wiki/Capacitance" title="Capacitance">capacitance</a> </td> <td style="text-align:center;">kg−1⋅m−2⋅s4⋅A2 </td> <td style="text-align:center;">C/V = C2/J </td></tr> <tr> <th scope="row"><a href="/wiki/Ohm_(unit)" class="mw-redirect" title="Ohm (unit)">ohm</a> </th> <td style="text-align:center;">Ω </td> <td><a href="/wiki/Electrical_resistance" class="mw-redirect" title="Electrical resistance">resistance</a> </td> <td style="text-align:center;">kg⋅m2⋅s−3⋅A−2 </td> <td style="text-align:center;">V/A = J⋅s/C2 </td></tr> <tr> <th scope="row"><a href="/wiki/Siemens_(unit)" title="Siemens (unit)">siemens</a> </th> <td style="text-align:center;">S </td> <td><a href="/wiki/Electrical_conductance" class="mw-redirect" title="Electrical conductance">electrical conductance</a> </td> <td style="text-align:center;">kg−1⋅m−2⋅s3⋅A2 </td> <td style="text-align:center;">Ω−1 </td></tr> <tr> <th scope="row"><a href="/wiki/Weber_(unit)" title="Weber (unit)">weber</a> </th> <td style="text-align:center;">Wb </td> <td><a href="/wiki/Magnetic_flux" title="Magnetic flux">magnetic flux</a> </td> <td style="text-align:center;">kg⋅m2⋅s−2⋅A−1 </td> <td style="text-align:center;">V⋅s </td></tr> <tr> <th scope="row"><a href="/wiki/Tesla_(unit)" title="Tesla (unit)">tesla</a> </th> <td style="text-align:center;">T </td> <td><a href="/wiki/Magnetic_flux_density" class="mw-redirect" title="Magnetic flux density">magnetic flux density</a> </td> <td style="text-align:center;">kg⋅s−2⋅A−1 </td> <td style="text-align:center;">Wb/m2 </td></tr> <tr> <th scope="row"><a href="/wiki/Henry_(unit)" title="Henry (unit)">henry</a> </th> <td style="text-align:center;">H </td> <td><a href="/wiki/Inductance" title="Inductance">inductance</a> </td> <td style="text-align:center;">kg⋅m2⋅s−2⋅A−2 </td> <td style="text-align:center;">Wb/A </td></tr> <tr> <th scope="row"><a href="/wiki/Degree_Celsius" class="mw-redirect" title="Degree Celsius">degree Celsius</a> </th> <td style="text-align:center;">°C </td> <td><a href="/wiki/Temperature" title="Temperature">temperature</a> </td> <td style="text-align:center;">K </td> <td> </td></tr> <tr> <th scope="row"><a href="/wiki/Lumen_(unit)" title="Lumen (unit)">lumen</a> </th> <td style="text-align:center;">lm </td> <td><a href="/wiki/Luminous_flux" title="Luminous flux">luminous flux</a> </td> <td style="text-align:center;">cd⋅m2/m2 </td> <td style="text-align:center;">cd⋅sr </td></tr> <tr> <th scope="row"><a href="/wiki/Lux" title="Lux">lux</a> </th> <td style="text-align:center;">lx </td> <td><a href="/wiki/Illuminance" title="Illuminance">illuminance</a> </td> <td style="text-align:center;">cd⋅m2/m4 </td> <td style="text-align:center;">lm/m2 = cd⋅sr⋅m−2 </td></tr> <tr> <th scope="row"><a href="/wiki/Becquerel" title="Becquerel">becquerel</a> </th> <td style="text-align:center;">Bq </td> <td><a href="/wiki/Radioactive_decay" title="Radioactive decay">activity referred to a radionuclide</a> (decays per unit time) </td> <td style="text-align:center;">s−1 </td> <td> </td></tr> <tr> <th scope="row"><a href="/wiki/Gray_(unit)" title="Gray (unit)">gray</a> </th> <td style="text-align:center;">Gy </td> <td><a href="/wiki/Absorbed_dose" title="Absorbed dose">absorbed dose</a>, <a href="/wiki/Kerma_(physics)" title="Kerma (physics)">kerma</a> </td> <td style="text-align:center;">m2⋅s−2 </td> <td style="text-align:center;">J/kg </td></tr> <tr> <th scope="row"><a href="/wiki/Sievert" title="Sievert">sievert</a> </th> <td style="text-align:center;">Sv </td> <td><a href="/wiki/Equivalent_dose" title="Equivalent dose">equivalent dose</a> </td> <td style="text-align:center;">m2⋅s−2 </td> <td style="text-align:center;">J/kg </td></tr> <tr> <th scope="row"><a href="/wiki/Katal" title="Katal">katal</a> </th> <td style="text-align:center;">kat </td> <td><a href="/wiki/Catalytic_activity" class="mw-redirect" title="Catalytic activity">catalytic activity</a> </td> <td style="text-align:center;">mol⋅s−1 </td> <td> </td></tr> <tr> <td colspan="5">Notes <div class="mw-references-wrap"><ol class="references"> <li id="cite_note-:0-7">^ <a href="#cite_ref-:0_7-0">a</a> <a href="#cite_ref-:0_7-1">b</a> The radian and steradian are defined as dimensionless derived units. </li> </ol></div> </td></tr></tbody></table> <div style="clear:both;" class=""></div> The derived units in the SI are formed by powers, products, or quotients of the base units and are unlimited in number.<a href="#cite_note-SIBrochure-8">[5]</a>: 103 <a href="#cite_note-NIST330-6">[4]</a>: 14, 16  <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Physics_measurements_SI_units.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/e/e6/Physics_measurements_SI_units.png/220px-Physics_measurements_SI_units.png" decoding="async" width="220" height="297" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/e6/Physics_measurements_SI_units.png/330px-Physics_measurements_SI_units.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/e6/Physics_measurements_SI_units.png/440px-Physics_measurements_SI_units.png 2x" data-file-width="494" data-file-height="667" /></a><figcaption>Arrangement of the principal measurements in physics based on the mathematical manipulation of length, time, and mass</figcaption></figure> <a href="/wiki/Derived_unit" class="mw-redirect" title="Derived unit">Derived units</a> apply to some <a href="/wiki/Derived_quantity" class="mw-redirect" title="Derived quantity">derived quantities</a>, which may by definition be expressed in terms of <a href="/wiki/Base_quantity" class="mw-redirect" title="Base quantity">base quantities</a>, and thus are not independent; for example, <a href="/wiki/Electrical_conductance" class="mw-redirect" title="Electrical conductance">electrical conductance</a> is the inverse of <a href="/wiki/Electrical_resistance" class="mw-redirect" title="Electrical resistance">electrical resistance</a>, with the consequence that the siemens is the inverse of the ohm, and similarly, the ohm and siemens can be replaced with a ratio of an ampere and a volt, because those quantities bear a defined relationship to each other.<a href="#cite_note-9">[a]</a> Other useful derived quantities can be specified in terms of the SI base and derived units that have no named units in the SI, such as acceleration, which has the SI unit m/s2.<a href="#cite_note-SIBrochure9thEd-1">[1]</a>: 139  A combination of base and derived units may be used to express a derived unit. For example, the SI unit of <a href="/wiki/Force" title="Force">force</a> is the <a href="/wiki/Newton_(unit)" title="Newton (unit)">newton</a> (N), the SI unit of <a href="/wiki/Pressure" title="Pressure">pressure</a> is the <a href="/wiki/Pascal_(unit)" title="Pascal (unit)">pascal</a> (Pa) – and the pascal can be defined as one newton per square metre (N/m2).<a href="#cite_note-10">[6]</a> <div class="mw-heading mw-heading3"><h3 id="Prefixes">Prefixes</h3>[<a href="/w/index.php?title=International_System_of_Units&action=edit&section=5" title="Edit section: Prefixes">edit</a>]</div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Metric_prefix" title="Metric prefix">Metric prefix</a></div> Like all metric systems, the SI uses <a href="/wiki/Metric_prefix" title="Metric prefix">metric prefixes</a> to systematically construct, for the same physical quantity, a set of units that are decimal multiples of each other over a wide range. For example, driving distances are normally given in <a href="/wiki/Kilometre" title="Kilometre">kilometres</a> (symbol km) rather than in metres. Here the metric prefix '<a href="/wiki/Kilo-" title="Kilo-">kilo-</a>' (symbol 'k') stands for a factor of 1000; thus, 1 km = 1000 m. The SI provides twenty-four metric prefixes that signify decimal powers ranging from 10−30 to 1030, the most recent being adopted in 2022.<a href="#cite_note-SIBrochure9thEd-1">[1]</a>: 143–144 <a href="#cite_note-11">[7]</a><a href="#cite_note-12">[8]</a><a href="#cite_note-13">[9]</a> Most prefixes correspond to integer powers of 1000; the only ones that do not are those for 10, 1/10, 100, and 1/100. The conversion between different SI units for one and the same physical quantity is always through a power of ten. This is why the SI (and metric systems more generally) are called decimal systems of measurement units.<a href="#cite_note-DecimalSystem-14">[10]</a> The grouping formed by a prefix symbol attached to a unit symbol (e.g. 'km', 'cm') constitutes a new inseparable unit symbol. This new symbol can be raised to a positive or negative power. It can also be combined with other unit symbols to form compound unit symbols.<a href="#cite_note-SIBrochure9thEd-1">[1]</a>: 143  For example, g/cm3 is an SI unit of <a href="/wiki/Density" title="Density">density</a>, where cm3 is to be interpreted as (cm)3. Prefixes are added to unit names to produce multiples and <a href="/wiki/Submultiple" class="mw-redirect" title="Submultiple">submultiples</a> of the original unit. All of these are integer powers of ten, and above a hundred or below a hundredth all are integer powers of a thousand. For example, kilo- denotes a multiple of a thousand and milli- denotes a multiple of a thousandth, so there are one thousand millimetres to the metre and one thousand metres to the kilometre. The prefixes are never combined, so for example a millionth of a metre is a micrometre, not a millimillimetre. Multiples of the kilogram are named as if the gram were the base unit, so a millionth of a kilogram is a milligram, not a microkilogram.<a href="#cite_note-SIBrochure-8">[5]</a>: 122 <a href="#cite_note-NIST811-15">[11]</a>: 14  The BIPM specifies 24 prefixes for the International System of Units (SI): <table class="wikitable" style="padding: 0; text-align: center; width: 0"> <caption><style data-mw-deduplicate="TemplateStyles:r1045256916">.mw-parser-output .navbar-header{text-align:center;position:relative;white-space:nowrap}.mw-parser-output .navbar-header .navbar{position:absolute;right:0;top:0;margin:0 5px}</style><div class="navbar-header"><a href="/wiki/Metric_prefix" title="Metric prefix">SI prefixes</a><style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist li{margin:0;display:inline}.mw-parser-output .hlist.inline,.mw-parser-output .hlist.inline dl,.mw-parser-output .hlist.inline ol,.mw-parser-output .hlist.inline ul,.mw-parser-output .hlist dl dl,.mw-parser-output .hlist dl ol,.mw-parser-output .hlist dl ul,.mw-parser-output .hlist ol dl,.mw-parser-output .hlist ol ol,.mw-parser-output .hlist ol ul,.mw-parser-output .hlist ul dl,.mw-parser-output .hlist ul ol,.mw-parser-output .hlist ul ul{display:inline}.mw-parser-output .hlist .mw-empty-li{display:none}.mw-parser-output .hlist dt::after{content:": "}.mw-parser-output .hlist dd::after,.mw-parser-output .hlist li::after{content:" · ";font-weight:bold}.mw-parser-output .hlist dd:last-child::after,.mw-parser-output .hlist dt:last-child::after,.mw-parser-output .hlist li:last-child::after{content:none}.mw-parser-output .hlist dd dd:first-child::before,.mw-parser-output .hlist dd dt:first-child::before,.mw-parser-output .hlist dd li:first-child::before,.mw-parser-output .hlist dt dd:first-child::before,.mw-parser-output .hlist dt dt:first-child::before,.mw-parser-output .hlist dt li:first-child::before,.mw-parser-output .hlist li dd:first-child::before,.mw-parser-output .hlist li dt:first-child::before,.mw-parser-output .hlist li li:first-child::before{content:" (";font-weight:normal}.mw-parser-output .hlist dd dd:last-child::after,.mw-parser-output .hlist dd dt:last-child::after,.mw-parser-output .hlist dd li:last-child::after,.mw-parser-output .hlist dt dd:last-child::after,.mw-parser-output .hlist dt dt:last-child::after,.mw-parser-output .hlist dt li:last-child::after,.mw-parser-output .hlist li dd:last-child::after,.mw-parser-output .hlist li dt:last-child::after,.mw-parser-output .hlist li li:last-child::after{content:")";font-weight:normal}.mw-parser-output .hlist ol{counter-reset:listitem}.mw-parser-output .hlist ol>li{counter-increment:listitem}.mw-parser-output .hlist ol>li::before{content:" "counter(listitem)"\a0 "}.mw-parser-output .hlist dd ol>li:first-child::before,.mw-parser-output .hlist dt ol>li:first-child::before,.mw-parser-output .hlist li ol>li:first-child::before{content:" ("counter(listitem)"\a0 "}</style><style data-mw-deduplicate="TemplateStyles:r1239400231">.mw-parser-output .navbar{display:inline;font-size:88%;font-weight:normal}.mw-parser-output .navbar-collapse{float:left;text-align:left}.mw-parser-output .navbar-boxtext{word-spacing:0}.mw-parser-output .navbar ul{display:inline-block;white-space:nowrap;line-height:inherit}.mw-parser-output .navbar-brackets::before{margin-right:-0.125em;content:"[ "}.mw-parser-output .navbar-brackets::after{margin-left:-0.125em;content:" ]"}.mw-parser-output .navbar li{word-spacing:-0.125em}.mw-parser-output .navbar a>span,.mw-parser-output .navbar a>abbr{text-decoration:inherit}.mw-parser-output .navbar-mini abbr{font-variant:small-caps;border-bottom:none;text-decoration:none;cursor:inherit}.mw-parser-output .navbar-ct-full{font-size:114%;margin:0 7em}.mw-parser-output .navbar-ct-mini{font-size:114%;margin:0 4em}html.skin-theme-clientpref-night .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}@media(prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}}@media print{.mw-parser-output .navbar{display:none!important}}</style><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:SI_prefixes_(infobox)" title="Template:SI prefixes (infobox)"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:SI_prefixes_(infobox)" title="Template talk:SI prefixes (infobox)"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:SI_prefixes_(infobox)" title="Special:EditPage/Template:SI prefixes (infobox)"><abbr title="Edit this template">e</abbr></a></li></ul></div></div> </caption> <tbody><tr> <th colspan="2">Prefix</th> <th rowspan="2">Base 10 </th> <th rowspan="2"><a href="/wiki/Decimal" title="Decimal">Decimal</a> </th> <th rowspan="2">Adoption <a href="#cite_note-16">[nb 1]</a> </th></tr> <tr> <th>Name</th> <th>Symbol </th></tr> <tr> <td>quetta</td> <td>Q</td> <td style="text-align:left;"><a href="/wiki/Orders_of_magnitude_(numbers)#1030" title="Orders of magnitude (numbers)">1030</a> </td> <td style="text-align:right; font-variant-numeric: tabular-nums;">1000000000000000000000000000000</td> <td rowspan="2">2022<a href="#cite_note-newUnitAdoption-17">[12]</a> </td></tr> <tr> <td>ronna</td> <td>R</td> <td style="text-align:left;"><a href="/wiki/Orders_of_magnitude_(numbers)#1027" title="Orders of magnitude (numbers)">1027</a> </td> <td style="text-align:right; font-variant-numeric: tabular-nums;">1000000000000000000000000000 </td></tr> <tr> <td>yotta</td> <td>Y</td> <td style="text-align:left;"><a href="/wiki/Orders_of_magnitude_(numbers)#1024" title="Orders of magnitude (numbers)">1024</a> </td> <td style="text-align:right; font-variant-numeric: tabular-nums;">1000000000000000000000000</td> <td rowspan="2">1991 </td></tr> <tr> <td>zetta</td> <td>Z</td> <td style="text-align:left;"><a href="/wiki/Orders_of_magnitude_(numbers)#1021" title="Orders of magnitude (numbers)">1021</a> </td> <td style="text-align:right; font-variant-numeric: tabular-nums;">1000000000000000000000 </td></tr> <tr> <td>exa</td> <td>E</td> <td style="text-align:left;"><a href="/wiki/Orders_of_magnitude_(numbers)#1018" title="Orders of magnitude (numbers)">1018</a> </td> <td style="text-align:right; font-variant-numeric: tabular-nums;">1000000000000000000</td> <td rowspan="2">1975<a href="#cite_note-18">[13]</a> </td></tr> <tr> <td>peta</td> <td>P</td> <td style="text-align:left;"><a href="/wiki/Orders_of_magnitude_(numbers)#1015" title="Orders of magnitude (numbers)">1015</a> </td> <td style="text-align:right; font-variant-numeric: tabular-nums;">1000000000000000 </td></tr> <tr> <td>tera</td> <td>T</td> <td style="text-align:left;"><a href="/wiki/Orders_of_magnitude_(numbers)#1012" title="Orders of magnitude (numbers)">1012</a> </td> <td style="text-align:right; font-variant-numeric: tabular-nums;">1000000000000</td> <td rowspan="2">1960 </td></tr> <tr> <td><a href="/wiki/Giga-" title="Giga-">giga</a></td> <td>G</td> <td style="text-align:left;"><a href="/wiki/1,000,000,000" title="1,000,000,000">109</a> </td> <td style="text-align:right; font-variant-numeric: tabular-nums;">1000000000 </td></tr> <tr> <td><a href="/wiki/Mega-" title="Mega-">mega</a></td> <td>M</td> <td style="text-align:left;"><a href="/wiki/1,000,000" title="1,000,000">106</a> </td> <td style="text-align:right; font-variant-numeric: tabular-nums;">1000000</td> <td>1873 </td></tr> <tr> <td><a href="/wiki/Kilo-" title="Kilo-">kilo</a></td> <td>k</td> <td style="text-align:left;"><a href="/wiki/1000_(number)" title="1000 (number)">103</a> </td> <td style="text-align:right; font-variant-numeric: tabular-nums;">1000</td> <td rowspan="3">1795 </td></tr> <tr> <td><a href="/wiki/Hecto-" title="Hecto-">hecto</a></td> <td>h</td> <td style="text-align:left;"><a href="/wiki/100" title="100">102</a></td> <td style="text-align:right; font-variant-numeric: tabular-nums;">100 </td></tr> <tr> <td><a href="/wiki/Deca-" title="Deca-">deca</a></td> <td>da</td> <td style="text-align:left;"><a href="/wiki/10" title="10">101</a></td> <td style="text-align:right; font-variant-numeric: tabular-nums;">10 </td></tr> <tr style="background:#EAECF0;color:black;"> <td>—</td> <td>—</td> <td style="text-align:left;"><a href="/wiki/1" title="1">100</a></td> <td style="font-variant-numeric: tabular-nums;">1</td> <td>— </td></tr> <tr> <td><a href="/wiki/Deci-" title="Deci-">deci</a></td> <td>d</td> <td style="text-align:left;"><a href="/wiki/Orders_of_magnitude_(numbers)#10-1" title="Orders of magnitude (numbers)">10−1</a> </td> <td style="text-align:left; font-variant-numeric: tabular-nums;">0.1</td> <td rowspan="3">1795 </td></tr> <tr> <td><a href="/wiki/Centi-" title="Centi-">centi</a></td> <td>c</td> <td style="text-align:left;"><a href="/wiki/Orders_of_magnitude_(numbers)#10−2" title="Orders of magnitude (numbers)">10−2</a> </td> <td style="text-align:left; font-variant-numeric: tabular-nums;">0.01 </td></tr> <tr> <td><a href="/wiki/Milli-" title="Milli-">milli</a></td> <td>m</td> <td style="text-align:left;"><a href="/wiki/Orders_of_magnitude_(numbers)#10−3" title="Orders of magnitude (numbers)">10−3</a> </td> <td style="text-align:left; font-variant-numeric: tabular-nums;">0.001 </td></tr> <tr> <td><a href="/wiki/Micro-" title="Micro-">micro</a></td> <td>μ</td> <td style="text-align:left;"><a href="/wiki/Orders_of_magnitude_(numbers)#10−6" title="Orders of magnitude (numbers)">10−6</a> </td> <td style="text-align:left; font-variant-numeric: tabular-nums;">0.000001</td> <td>1873 </td></tr> <tr> <td><a href="/wiki/Nano-" title="Nano-">nano</a></td> <td>n</td> <td style="text-align:left;"><a href="/wiki/Orders_of_magnitude_(numbers)#10−9" title="Orders of magnitude (numbers)">10−9</a> </td> <td style="text-align:left; font-variant-numeric: tabular-nums;">0.000000001</td> <td rowspan="2">1960 </td></tr> <tr> <td>pico</td> <td>p</td> <td style="text-align:left;"><a href="/wiki/Orders_of_magnitude_(numbers)#10−12" title="Orders of magnitude (numbers)">10−12</a> </td> <td style="text-align:left; font-variant-numeric: tabular-nums;">0.000000000001 </td></tr> <tr> <td>femto</td> <td>f</td> <td style="text-align:left;"><a href="/wiki/Orders_of_magnitude_(numbers)#10−15" title="Orders of magnitude (numbers)">10−15</a> </td> <td style="text-align:left; font-variant-numeric: tabular-nums;">0.000000000000001</td> <td rowspan="2">1964 </td></tr> <tr> <td>atto</td> <td>a</td> <td style="text-align:left;"><a href="/wiki/Orders_of_magnitude_(numbers)#10−18" title="Orders of magnitude (numbers)">10−18</a> </td> <td style="text-align:left; font-variant-numeric: tabular-nums;">0.000000000000000001 </td></tr> <tr> <td>zepto</td> <td>z</td> <td style="text-align:left;"><a href="/wiki/Orders_of_magnitude_(numbers)#10−21" title="Orders of magnitude (numbers)">10−21</a> </td> <td style="text-align:left; font-variant-numeric: tabular-nums;">0.000000000000000000001</td> <td rowspan="2">1991 </td></tr> <tr> <td>yocto</td> <td>y</td> <td style="text-align:left;"><a href="/wiki/Orders_of_magnitude_(numbers)#10−24" title="Orders of magnitude (numbers)">10−24</a> </td> <td style="text-align:left; font-variant-numeric: tabular-nums;">0.000000000000000000000001 </td></tr> <tr> <td>ronto</td> <td>r</td> <td style="text-align:left;"><a href="/wiki/Orders_of_magnitude_(numbers)#10−27" title="Orders of magnitude (numbers)">10−27</a> </td> <td style="text-align:left; font-variant-numeric: tabular-nums;">0.000000000000000000000000001</td> <td rowspan="2">2022<a href="#cite_note-newUnitAdoption-17">[12]</a> </td></tr> <tr> <td>quecto</td> <td>q</td> <td style="text-align:left;"><a href="/wiki/Orders_of_magnitude_(numbers)#10−30" title="Orders of magnitude (numbers)">10−30</a> </td> <td style="text-align:left; font-variant-numeric: tabular-nums;">0.000000000000000000000000000001 </td></tr> <tr> <td style="text-align: left;" colspan="5"> <dl><dt>Notes</dt></dl> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239543626"><div class="reflist"> <div class="mw-references-wrap"><ol class="references"> <li id="cite_note-16"><a href="#cite_ref-16">^</a> Prefixes adopted before 1960 already existed before SI. The introduction of the <a href="/wiki/Centimetre%E2%80%93gram%E2%80%93second_system_of_units" title="Centimetre–gram–second system of units">CGS system</a> was in 1873. </li> </ol></div></div> </td></tr></tbody></table> <div class="mw-heading mw-heading3"><h3 id="Coherent_and_non-coherent_SI_units">Coherent and non-coherent SI units </h3>[<a href="/w/index.php?title=International_System_of_Units&action=edit&section=6" title="Edit section: Coherent and non-coherent SI units">edit</a>]</div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Further information: <a href="/wiki/Coherent_unit" class="mw-redirect" title="Coherent unit">Coherent unit</a></div> The base units and the derived units formed as the product of powers of the base units with a numerical factor of one form a <a href="/wiki/Coherent_system_of_units" class="mw-redirect" title="Coherent system of units">coherent system of units</a>. Every physical quantity has exactly one coherent SI unit. For example, 1 m/s = 1 m / (1 s) is the coherent derived unit for velocity.<a href="#cite_note-SIBrochure9thEd-1">[1]</a>: 139  With the exception of the kilogram (for which the prefix kilo- is required for a coherent unit), when prefixes are used with the coherent SI units, the resulting units are no longer coherent, because the prefix introduces a numerical factor other than one.<a href="#cite_note-SIBrochure9thEd-1">[1]</a>: 137  For example, the metre, kilometre, centimetre, nanometre, etc. are all SI units of length, though only the metre is a coherent SI unit. The complete set of SI units consists of both the coherent set and the multiples and sub-multiples of coherent units formed by using the SI prefixes.<a href="#cite_note-SIBrochure9thEd-1">[1]</a>: 138  The kilogram is the only coherent SI unit whose name and symbol include a prefix. For historical reasons, the names and symbols for multiples and sub-multiples of the unit of mass are formed as if the <a href="/wiki/Gram" title="Gram">gram</a> were the base unit. Prefix names and symbols are attached to the unit name gram and the unit symbol g respectively. For example, 10−6 kg is written milligram and mg, not microkilogram and μkg.<a href="#cite_note-SIBrochure9thEd-1">[1]</a>: 144  Several different quantities may share the same coherent SI unit. For example, the joule per kelvin (symbol J/K) is the coherent SI unit for two distinct quantities: <a href="/wiki/Heat_capacity" title="Heat capacity">heat capacity</a> and <a href="/wiki/Entropy" title="Entropy">entropy</a>; another example is the ampere, which is the coherent SI unit for both <a href="/wiki/Electric_current" title="Electric current">electric current</a> and <a href="/wiki/Magnetomotive_force" title="Magnetomotive force">magnetomotive force</a>. This illustrates why it is important not to use the unit alone to specify the quantity. As the SI Brochure states,<a href="#cite_note-SIBrochure9thEd-1">[1]</a>: 140  "this applies not only to technical texts, but also, for example, to measuring instruments (i.e. the instrument read-out needs to indicate both the unit and the quantity measured)". Furthermore, the same coherent SI unit may be a base unit in one context, but a coherent derived unit in another. For example, the ampere is a base unit when it is a unit of electric current, but a coherent derived unit when it is a unit of magnetomotive force.<a href="#cite_note-SIBrochure9thEd-1">[1]</a>: 140  <table class="wikitable floatleft" style="margin:1em auto 1em auto;line-height:1.4"> <caption><big>Examples of coherent derived units in terms of base units</big><a href="#cite_note-NIST330-6">[4]</a>: 17  </caption> <tbody><tr> <th scope="col">Name </th> <th scope="col">Symbol </th> <th scope="col">Derived quantity </th> <th scope="col">Typical symbol </th></tr> <tr> <th scope="row"><a href="/wiki/Square_metre" title="Square metre">square metre</a> </th> <td style="text-align:center;">m2 </td> <td><a href="/wiki/Area" title="Area">area</a> </td> <td style="text-align:center;">A </td></tr> <tr> <th scope="row"><a href="/wiki/Cubic_metre" title="Cubic metre">cubic metre</a> </th> <td style="text-align:center;">m3 </td> <td><a href="/wiki/Volume" title="Volume">volume</a> </td> <td style="text-align:center;">V </td></tr> <tr> <th scope="row"><a href="/wiki/Metre_per_second" title="Metre per second">metre per second</a> </th> <td style="text-align:center;">m/s </td> <td><a href="/wiki/Speed" title="Speed">speed</a>, <a href="/wiki/Velocity" title="Velocity">velocity</a> </td> <td style="text-align:center;">v </td></tr> <tr> <th scope="row"><a href="/wiki/Metre_per_second_squared" title="Metre per second squared">metre per second squared</a> </th> <td style="text-align:center;">m/s2 </td> <td><a href="/wiki/Acceleration" title="Acceleration">acceleration</a> </td> <td style="text-align:center;">a </td></tr> <tr> <th scope="row" rowspan="2"><a href="/wiki/Reciprocal_metre" class="mw-redirect" title="Reciprocal metre">reciprocal metre</a> </th> <td rowspan="2" style="text-align:center;">m−1 </td> <td><a href="/wiki/Wavenumber" title="Wavenumber">wavenumber</a> </td> <td style="text-align:center;">σ, ṽ </td></tr> <tr> <td><a href="/wiki/Vergence_(optics)" title="Vergence (optics)">vergence (optics)</a> </td> <td style="text-align:center;">V, 1/f </td></tr> <tr> <th scope="row"><a href="/wiki/Kilogram_per_cubic_metre" title="Kilogram per cubic metre">kilogram per cubic metre</a> </th> <td style="text-align:center;">kg/m3 </td> <td><a href="/wiki/Density" title="Density">density</a> </td> <td style="text-align:center;">ρ </td></tr> <tr> <th scope="row">kilogram per square metre </th> <td style="text-align:center;">kg/m2 </td> <td><a href="/wiki/Surface_density" class="mw-redirect" title="Surface density">surface density</a> </td> <td style="text-align:center;">ρA </td></tr> <tr> <th scope="row">cubic metre per kilogram </th> <td style="text-align:center;">m3/kg </td> <td><a href="/wiki/Specific_volume" title="Specific volume">specific volume</a> </td> <td style="text-align:center;">v </td></tr> <tr> <th scope="row">ampere per square metre </th> <td style="text-align:center;">A/m2 </td> <td><a href="/wiki/Current_density" title="Current density">current density</a> </td> <td style="text-align:center;">j </td></tr> <tr> <th scope="row"><a href="/wiki/Amperes_per_metre" class="mw-redirect" title="Amperes per metre">ampere per metre</a> </th> <td style="text-align:center;">A/m </td> <td><a href="/wiki/Magnetic_field_strength" class="mw-redirect" title="Magnetic field strength">magnetic field strength</a> </td> <td style="text-align:center;">H </td></tr> <tr> <th scope="row">mole per cubic metre </th> <td style="text-align:center;">mol/m3 </td> <td><a href="/wiki/Concentration" title="Concentration">concentration</a> </td> <td style="text-align:center;">c </td></tr> <tr> <th scope="row"><a href="/wiki/Kilogram_per_cubic_metre" title="Kilogram per cubic metre">kilogram per cubic metre</a> </th> <td style="text-align:center;">kg/m3 </td> <td><a href="/wiki/Mass_concentration_(chemistry)" title="Mass concentration (chemistry)">mass concentration</a> </td> <td style="text-align:center;">ρ, γ </td></tr> <tr> <th scope="row"><a href="/wiki/Candela_per_square_metre" title="Candela per square metre">candela per square metre</a> </th> <td style="text-align:center;">cd/m2 </td> <td><a href="/wiki/Luminance" title="Luminance">luminance</a> </td> <td style="text-align:center;">Lv </td></tr></tbody></table> <table class="wikitable floatleft" style="margin:1em auto 1em auto;line-height:1.4"> <caption><big>Examples of derived units that include units with special names</big><a href="#cite_note-NIST330-6">[4]</a>: 18  </caption> <tbody><tr> <th scope="col">Name </th> <th scope="col">Symbol </th> <th scope="col">Quantity </th> <th scope="col">In SI base units </th></tr> <tr> <th scope="row"><a href="/wiki/Pascal-second" class="mw-redirect" title="Pascal-second">pascal-second</a> </th> <td style="text-align:center;">Pa⋅s </td> <td><a href="/wiki/Dynamic_viscosity" class="mw-redirect" title="Dynamic viscosity">dynamic viscosity</a> </td> <td style="text-align:center;">m−1⋅kg⋅s−1 </td></tr> <tr> <th scope="row"><a href="/wiki/Newton-metre" title="Newton-metre">newton-metre</a> </th> <td style="text-align:center;">N⋅m </td> <td><a href="/wiki/Moment_of_force" class="mw-redirect" title="Moment of force">moment of force</a> </td> <td style="text-align:center;">m2⋅kg⋅s−2 </td></tr> <tr> <th scope="row">newton per metre </th> <td style="text-align:center;">N/m </td> <td><a href="/wiki/Surface_tension" title="Surface tension">surface tension</a> </td> <td style="text-align:center;">kg⋅s−2 </td></tr> <tr> <th scope="row"><a href="/wiki/Radian_per_second" title="Radian per second">radian per second</a> </th> <td style="text-align:center;">rad/s </td> <td><a href="/wiki/Angular_velocity" title="Angular velocity">angular velocity</a>, <a href="/wiki/Angular_frequency" title="Angular frequency">angular frequency</a> </td> <td style="text-align:center;">s−1 </td></tr> <tr> <th scope="row"><a href="/wiki/Radian_per_second_squared" class="mw-redirect" title="Radian per second squared">radian per second squared</a> </th> <td style="text-align:center;">rad/s2 </td> <td><a href="/wiki/Angular_acceleration" title="Angular acceleration">angular acceleration</a> </td> <td style="text-align:center;">s−2 </td></tr> <tr> <th scope="row"><a href="/wiki/Watt_per_square_metre" class="mw-redirect" title="Watt per square metre">watt per square metre</a> </th> <td style="text-align:center;">W/m2 </td> <td>heat flux density, <a href="/wiki/Irradiance" title="Irradiance">irradiance</a> </td> <td style="text-align:center;">kg⋅s−3 </td></tr> <tr> <th scope="row"><a href="/wiki/Joule_per_kelvin" class="mw-redirect" title="Joule per kelvin">joule per kelvin</a> </th> <td style="text-align:center;">J/K </td> <td><a href="/wiki/Entropy" title="Entropy">entropy</a>, <a href="/wiki/Heat_capacity" title="Heat capacity">heat capacity</a> </td> <td style="text-align:center;">m2⋅kg⋅s−2⋅K−1 </td></tr> <tr> <th scope="row">joule per kilogram-kelvin </th> <td style="text-align:center;">J/(kg⋅K) </td> <td><a href="/wiki/Specific_heat_capacity" title="Specific heat capacity">specific heat capacity</a>, <a href="/wiki/Specific_entropy" class="mw-redirect" title="Specific entropy">specific entropy</a> </td> <td style="text-align:center;">m2⋅s−2⋅K−1 </td></tr> <tr> <th scope="row">joule per kilogram </th> <td style="text-align:center;">J/kg </td> <td><a href="/wiki/Specific_energy" title="Specific energy">specific energy</a> </td> <td style="text-align:center;">m2⋅s−2 </td></tr> <tr> <th scope="row">watt per metre-kelvin </th> <td style="text-align:center;">W/(m⋅K) </td> <td><a href="/wiki/Thermal_conductivity" class="mw-redirect" title="Thermal conductivity">thermal conductivity</a> </td> <td style="text-align:center;">m⋅kg⋅s−3⋅K−1 </td></tr> <tr> <th scope="row">joule per cubic metre </th> <td style="text-align:center;">J/m3 </td> <td><a href="/wiki/Energy_density" title="Energy density">energy density</a> </td> <td style="text-align:center;">m−1⋅kg⋅s−2 </td></tr> <tr> <th scope="row">volt per metre </th> <td style="text-align:center;">V/m </td> <td><a href="/wiki/Electric_field_strength" class="mw-redirect" title="Electric field strength">electric field strength</a> </td> <td style="text-align:center;">m⋅kg⋅s−3⋅A−1 </td></tr> <tr> <th scope="row">coulomb per cubic metre </th> <td style="text-align:center;">C/m3 </td> <td><a href="/wiki/Electric_charge_density" class="mw-redirect" title="Electric charge density">electric charge density</a> </td> <td style="text-align:center;">m−3⋅s⋅A </td></tr> <tr> <th scope="row">coulomb per square metre </th> <td style="text-align:center;">C/m2 </td> <td><a href="/wiki/Surface_charge_density" class="mw-redirect" title="Surface charge density">surface charge density</a>, <a href="/wiki/Electric_flux_density" class="mw-redirect" title="Electric flux density">electric flux density</a>, <a href="/wiki/Electric_displacement" class="mw-redirect" title="Electric displacement">electric displacement</a> </td> <td style="text-align:center;">m−2⋅s⋅A </td></tr> <tr> <th scope="row">farad per metre </th> <td style="text-align:center;">F/m </td> <td><a href="/wiki/Permittivity" title="Permittivity">permittivity</a> </td> <td style="text-align:center;">m−3⋅kg−1⋅s4⋅A2 </td></tr> <tr> <th scope="row">henry per metre </th> <td style="text-align:center;">H/m </td> <td><a href="/wiki/Permeability_(electromagnetism)" title="Permeability (electromagnetism)">permeability</a> </td> <td style="text-align:center;">m⋅kg⋅s−2⋅A−2 </td></tr> <tr> <th scope="row">joule per mole </th> <td style="text-align:center;">J/mol </td> <td><a href="/wiki/Joule_per_mole" title="Joule per mole">molar energy</a> </td> <td style="text-align:center;">m2⋅kg⋅s−2⋅mol−1 </td></tr> <tr> <th scope="row">joule per mole-kelvin </th> <td style="text-align:center;">J/(mol⋅K) </td> <td><a href="/wiki/Molar_entropy" class="mw-redirect" title="Molar entropy">molar entropy</a>, <a href="/wiki/Molar_heat_capacity" title="Molar heat capacity">molar heat capacity</a> </td> <td style="text-align:center;">m2⋅kg⋅s−2⋅K−1⋅mol−1 </td></tr> <tr> <th scope="row">coulomb per kilogram </th> <td style="text-align:center;">C/kg </td> <td><a href="/wiki/Radiation_exposure" title="Radiation exposure">exposure</a> (x- and γ-rays) </td> <td style="text-align:center;">kg−1⋅s⋅A </td></tr> <tr> <th scope="row">gray per second </th> <td style="text-align:center;">Gy/s </td> <td><a href="/wiki/Absorbed_dose_rate" class="mw-redirect" title="Absorbed dose rate">absorbed dose rate</a> </td> <td style="text-align:center;">m2⋅s−3 </td></tr> <tr> <th scope="row">watt per steradian </th> <td style="text-align:center;">W/sr </td> <td><a href="/wiki/Radiant_intensity" title="Radiant intensity">radiant intensity</a> </td> <td style="text-align:center;">m2⋅kg⋅s−3 </td></tr> <tr> <th scope="row">watt per square metre-steradian </th> <td style="text-align:center;">W/(m2⋅sr) </td> <td><a href="/wiki/Radiance" title="Radiance">radiance</a> </td> <td style="text-align:center;">kg⋅s−3 </td></tr> <tr> <th scope="row">katal per cubic metre </th> <td style="text-align:center;">kat/m3 </td> <td><a href="/wiki/Catalytic_activity_concentration" class="mw-redirect" title="Catalytic activity concentration">catalytic activity concentration</a> </td> <td style="text-align:center;">m−3⋅s−1⋅mol </td></tr></tbody></table> <div style="clear:both;" class=""></div> <div class="mw-heading mw-heading2"><h2 id="Lexicographic_conventions">Lexicographic conventions </h2>[<a href="/w/index.php?title=International_System_of_Units&action=edit&section=7" title="Edit section: Lexicographic conventions">edit</a>]</div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">See also: <a href="/wiki/ISO_31-0#Typographic_conventions" title="ISO 31-0">ISO 31-0 § Typographic conventions</a>, and <a href="/wiki/Space_(punctuation)#Unit_symbols_and_numbers" title="Space (punctuation)">Space (punctuation) § Unit symbols and numbers</a></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:981ms2.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/0/0c/981ms2.png" decoding="async" width="200" height="85" class="mw-file-element" data-file-width="200" data-file-height="85" /></a><figcaption>Example of lexical conventions. In the expression of acceleration due to gravity, a space separates the value and the units, both the 'm' and the 's' are lowercase because neither the metre nor the second are named after people, and exponentiation is represented with a <a href="/wiki/Superscript" class="mw-redirect" title="Superscript">superscript</a> '2'.</figcaption></figure> <div class="mw-heading mw-heading3"><h3 id="Unit_names">Unit names</h3>[<a href="/w/index.php?title=International_System_of_Units&action=edit&section=8" title="Edit section: Unit names">edit</a>]</div> According to the SI Brochure,<a href="#cite_note-SIBrochure9thEd-1">[1]</a>: 148  unit names should be treated as <a href="/wiki/Common_noun" class="mw-redirect" title="Common noun">common nouns</a> of the context language. This means that they should be typeset in the same character set as other common nouns (e.g. <a href="/wiki/Latin_alphabet" title="Latin alphabet">Latin alphabet</a> in English, <a href="/wiki/Cyrillic_script" title="Cyrillic script">Cyrillic script</a> in Russian, etc.), following the usual grammatical and <a href="/wiki/Orthography" title="Orthography">orthographical</a> rules of the context language. For example, in English and French, even when the unit is named after a person and its symbol begins with a capital letter, the unit name in running text should start with a lowercase letter (e.g., newton, hertz, pascal) and is <a href="/wiki/Capitalised" class="mw-redirect" title="Capitalised">capitalised</a> only at the beginning of a sentence and in <a href="/wiki/Title_capitalization" class="mw-redirect" title="Title capitalization">headings and publication titles</a>. As a nontrivial application of this rule, the SI Brochure notes<a href="#cite_note-SIBrochure9thEd-1">[1]</a>: 148  that the name of the unit with the symbol °C is correctly spelled as 'degree <a href="/wiki/Celsius" title="Celsius">Celsius</a>': the first letter of the name of the unit, 'd', is in lowercase, while the modifier 'Celsius' is capitalised because it is a proper name.<a href="#cite_note-SIBrochure9thEd-1">[1]</a>: 148  The English spelling and even names for certain SI units and metric prefixes depend on the variety of English used. <a href="/wiki/US_English" class="mw-redirect" title="US English">US English</a> uses the spelling deka-, meter, and liter, and <a href="/wiki/International_English" title="International English">International English</a> uses deca-, metre, and litre. The name of the unit whose symbol is t and which is defined according to 1 t = 103 kg is 'metric ton' in US English and 'tonne' in International English.<a href="#cite_note-NIST330-6">[4]</a>: iii  <div class="mw-heading mw-heading3"><h3 id="Unit_symbols_and_the_values_of_quantities">Unit symbols and the values of quantities</h3>[<a href="/w/index.php?title=International_System_of_Units&action=edit&section=9" title="Edit section: Unit symbols and the values of quantities">edit</a>]</div> Symbols of SI units are intended to be unique and universal, independent of the context language.<a href="#cite_note-SIBrochure-8">[5]</a>: 130–135  The SI Brochure has specific rules for writing them.<a href="#cite_note-SIBrochure-8">[5]</a>: 130–135  In addition, the SI Brochure provides style conventions for among other aspects of displaying quantities units: the quantity symbols, formatting of numbers and the decimal marker, expressing measurement uncertainty, multiplication and division of quantity symbols, and the use of pure numbers and various angles.<a href="#cite_note-SIBrochure9thEd-1">[1]</a>: 147  In the United States, the guideline produced by the <a href="/wiki/National_Institute_of_Standards_and_Technology" title="National Institute of Standards and Technology">National Institute of Standards and Technology</a> (NIST)<a href="#cite_note-NIST811-15">[11]</a>: 37  clarifies language-specific details for American English that were left unclear by the SI Brochure, but is otherwise identical to the SI Brochure.<a href="#cite_note-NISTInterprepation-19">[14]</a> For example, since 1979, the <a href="/wiki/Litre" title="Litre">litre</a> may exceptionally be written using either an uppercase "L" or a lowercase "l", a decision prompted by the similarity of the lowercase letter "l" to the numeral "1", especially with certain typefaces or English-style handwriting. The American NIST recommends that within the United States "L" be used rather than "l".<a href="#cite_note-NIST811-15">[11]</a> <div class="mw-heading mw-heading2"><h2 id="Realisation_of_units">Realisation of units </h2>[<a href="/w/index.php?title=International_System_of_Units&action=edit&section=10" title="Edit section: Realisation of units">edit</a>]</div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Realisation_(metrology)" title="Realisation (metrology)">Realisation (metrology)</a></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Silicon_sphere_for_Avogadro_project.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/4/41/Silicon_sphere_for_Avogadro_project.jpg/170px-Silicon_sphere_for_Avogadro_project.jpg" decoding="async" width="170" height="233" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/41/Silicon_sphere_for_Avogadro_project.jpg/255px-Silicon_sphere_for_Avogadro_project.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/4/41/Silicon_sphere_for_Avogadro_project.jpg/340px-Silicon_sphere_for_Avogadro_project.jpg 2x" data-file-width="631" data-file-height="863" /></a><figcaption>Silicon sphere for the <a href="/wiki/Avogadro_project" class="mw-redirect" title="Avogadro project">Avogadro project</a> used for measuring the Avogadro constant to a relative <a href="/wiki/Standard_uncertainty" class="mw-redirect" title="Standard uncertainty">standard uncertainty</a> of 2×10−8 or less, held by <a href="/wiki/Achim_Leistner" title="Achim Leistner">Achim Leistner</a><a href="#cite_note-20">[15]</a></figcaption></figure> Metrologists carefully distinguish between the definition of a unit and its realisation. The SI units are defined by declaring that seven defining constants<a href="#cite_note-SIBrochure9thEd-1">[1]</a>: 125–129  have certain exact numerical values when expressed in terms of their SI units. The realisation of the definition of a unit is the procedure by which the definition may be used to establish the value and associated uncertainty of a quantity of the same kind as the unit.<a href="#cite_note-SIBrochure9thEd-1">[1]</a>: 135  For each base unit the BIPM publishes a mises en pratique, (<a href="/wiki/French_language" title="French language">French</a> for 'putting into practice; implementation',<a href="#cite_note-NIST_mise_en_pratique-21">[16]</a>) describing the current best practical realisations of the unit.<a href="#cite_note-MisesEnPratique-22">[17]</a> The separation of the defining constants from the definitions of units means that improved measurements can be developed leading to changes in the mises en pratique as science and technology develop, without having to revise the definitions. The published mise en pratique is not the only way in which a base unit can be determined: the SI Brochure states that "any method consistent with the laws of physics could be used to realise any SI unit".<a href="#cite_note-SIBrochure-8">[5]</a>: 111  Various consultative committees of the <a href="/wiki/CIPM" class="mw-redirect" title="CIPM">CIPM</a> decided in 2016 that more than one mise en pratique would be developed for determining the value of each unit.<a href="#cite_note-23">[18]</a> These methods include the following: <ul><li>At least three separate experiments be carried out yielding values having a relative <a href="/wiki/Standard_uncertainty" class="mw-redirect" title="Standard uncertainty">standard uncertainty</a> in the determination of the <a href="/wiki/Kilogram" title="Kilogram">kilogram</a> of no more than 5×10−8 and at least one of these values should be better than 2×10−8. Both the <a href="/wiki/Kibble_balance" title="Kibble balance">Kibble balance</a> and the <a href="/wiki/Avogadro_project" class="mw-redirect" title="Avogadro project">Avogadro project</a> should be included in the experiments and any differences between these be reconciled.<a href="#cite_note-24">[19]</a><a href="#cite_note-25">[20]</a></li> <li>The definition of the <a href="/wiki/Kelvin" title="Kelvin">kelvin</a> measured with a relative uncertainty of the <a href="/wiki/Boltzmann_constant" title="Boltzmann constant">Boltzmann constant</a> derived from two fundamentally different methods such as acoustic gas <a href="/wiki/Thermometry" class="mw-redirect" title="Thermometry">thermometry</a> and dielectric constant gas thermometry be better than one part in 10−6 and that these values be corroborated by other measurements.<a href="#cite_note-26">[21]</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="Organizational_status">Organizational status</h2>[<a href="/w/index.php?title=International_System_of_Units&action=edit&section=11" title="Edit section: Organizational status">edit</a>]</div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Metric_and_imperial_systems_(2019).svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/0/08/Metric_and_imperial_systems_%282019%29.svg/290px-Metric_and_imperial_systems_%282019%29.svg.png" decoding="async" width="290" height="147" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/08/Metric_and_imperial_systems_%282019%29.svg/435px-Metric_and_imperial_systems_%282019%29.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/08/Metric_and_imperial_systems_%282019%29.svg/580px-Metric_and_imperial_systems_%282019%29.svg.png 2x" data-file-width="2754" data-file-height="1398" /></a><figcaption>Countries using the <a href="/wiki/Metric_system" title="Metric system">metric</a> (SI), <a href="/wiki/Imperial_units" title="Imperial units">imperial</a>, and <a href="/wiki/US_customary" class="mw-redirect" title="US customary">US customary</a> systems as of 2019</figcaption></figure> The International System of Units, or SI,<a href="#cite_note-SIBrochure9thEd-1">[1]</a>: <span title="Page: 123
Quotation: "... since its establishment in 1960, the International System of Units has always been referred to as "the SI" in its shortened form."" class="tooltip tooltip-dashed" style="border-bottom: 1px dashed;">123  is a <a href="/wiki/Decimal" title="Decimal">decimal</a> and <a href="/wiki/Metric_system" title="Metric system">metric</a> <a href="/wiki/System_of_units" class="mw-redirect" title="System of units">system of units</a> established in 1960 and periodically updated since then. The SI has an <a href="/wiki/Metrication" title="Metrication">official status</a> in most countries, including <a href="/wiki/Metrication_in_the_United_States" title="Metrication in the United States">the United States</a>, <a href="/wiki/Metrication_in_Canada" title="Metrication in Canada">Canada</a>, and <a href="/wiki/Metrication_in_the_United_Kingdom" title="Metrication in the United Kingdom">the United Kingdom</a>, although these three countries are among the handful of nations that, to various degrees, also continue to use their customary systems. Nevertheless, with this nearly universal level of acceptance, the SI "has been used around the world as the preferred system of units, the basic language for science, technology, industry, and trade."<a href="#cite_note-SIBrochure9thEd-1">[1]</a>: 123, 126  The only other types of measurement system that still have widespread use across the world are the <a href="/wiki/Imperial_and_US_customary_measurement_systems" title="Imperial and US customary measurement systems">imperial and US customary measurement systems</a>. The <a href="/wiki/International_yard_and_pound" title="International yard and pound">international yard and pound</a> are defined in terms of the SI.<a href="#cite_note-Standards1959-27">[22]</a> <div class="mw-heading mw-heading3"><h3 id="International_System_of_Quantities">International System of Quantities</h3>[<a href="/w/index.php?title=International_System_of_Units&action=edit&section=12" title="Edit section: International System of Quantities">edit</a>]</div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/International_System_of_Quantities" title="International System of Quantities">International System of Quantities</a></div> The quantities and equations that provide the context in which the SI units are defined are now referred to as the <a href="/wiki/International_System_of_Quantities" title="International System of Quantities">International System of Quantities</a> (ISQ). The ISQ is based on the <a href="/wiki/Quantity#Quantity_in_physical_science" title="Quantity">quantities</a> underlying each of the <a href="/wiki/SI_base_units" class="mw-redirect" title="SI base units">seven base units of the SI</a>. Other quantities, such as <a href="/wiki/Area" title="Area">area</a>, <a href="/wiki/Pressure" title="Pressure">pressure</a>, and <a href="/wiki/Electrical_resistance" class="mw-redirect" title="Electrical resistance">electrical resistance</a>, are derived from these base quantities by clear, non-contradictory equations. The ISQ defines the quantities that are measured with the SI units.<a href="#cite_note-28">[23]</a> The ISQ is formalised, in part, in the international standard <a href="/wiki/ISO/IEC_80000" title="ISO/IEC 80000">ISO/IEC 80000</a>, which was completed in 2009 with the publication of <a href="/wiki/ISO_80000-1" class="mw-redirect" title="ISO 80000-1">ISO 80000-1</a>,<a href="#cite_note-29">[24]</a> and has largely been revised in 2019–2020.<a href="#cite_note-30">[25]</a> <div class="mw-heading mw-heading3"><h3 id="Controlling_authority">Controlling authority</h3>[<a href="/w/index.php?title=International_System_of_Units&action=edit&section=13" title="Edit section: Controlling authority">edit</a>]</div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main articles: <a href="/wiki/General_Conference_on_Weights_and_Measures" title="General Conference on Weights and Measures">General Conference on Weights and Measures</a> and <a href="/wiki/International_Bureau_of_Weights_and_Measures" title="International Bureau of Weights and Measures">International Bureau of Weights and Measures</a></div> The SI is regulated and continually developed by three international organisations that were established in 1875 under the terms of the <a href="/wiki/Metre_Convention" title="Metre Convention">Metre Convention</a>. They are the <a href="/wiki/General_Conference_on_Weights_and_Measures" title="General Conference on Weights and Measures">General Conference on Weights and Measures</a> (CGPM<a href="#cite_note-French_CGPM-31">[b]</a>),<a href="#cite_note-FR_Interpretation_of_the_SI-32">[26]</a> the International Committee for Weights and Measures (CIPM<a href="#cite_note-French_CIPM-33">[c]</a>), and the <a href="/wiki/International_Bureau_of_Weights_and_Measures" title="International Bureau of Weights and Measures">International Bureau of Weights and Measures</a> (BIPM<a href="#cite_note-BIPM_from_French-34">[d]</a>). All the decisions and recommendations concerning units are collected in a brochure called The International System of Units (SI),<a href="#cite_note-SIBrochure9thEd-1">[1]</a> which is published in French and English by the BIPM and periodically updated. The writing and maintenance of the brochure is carried out by one of the committees of the CIPM. The definitions of the terms "quantity", "unit", "dimension", etc. that are used in the SI Brochure are those given in the <a href="/wiki/International_vocabulary_of_metrology" class="mw-redirect" title="International vocabulary of metrology">international vocabulary of metrology</a>.<a href="#cite_note-35">[27]</a> The brochure leaves some scope for local variations, particularly regarding unit names and terms in different languages. For example, the United States' <a href="/wiki/National_Institute_of_Standards_and_Technology" title="National Institute of Standards and Technology">National Institute of Standards and Technology</a> (NIST) has produced a version of the CGPM document (NIST SP 330) which clarifies usage for English-language publications that use <a href="/wiki/American_English" title="American English">American English</a>.<a href="#cite_note-NIST330-6">[4]</a> <div class="mw-heading mw-heading2"><h2 id="History">History</h2>[<a href="/w/index.php?title=International_System_of_Units&action=edit&section=14" title="Edit section: History">edit</a>]</div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Alter_Grenzstein_Pontebba_01.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/e/e4/Alter_Grenzstein_Pontebba_01.jpg/170px-Alter_Grenzstein_Pontebba_01.jpg" decoding="async" width="170" height="256" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/e4/Alter_Grenzstein_Pontebba_01.jpg/255px-Alter_Grenzstein_Pontebba_01.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/e4/Alter_Grenzstein_Pontebba_01.jpg/340px-Alter_Grenzstein_Pontebba_01.jpg 2x" data-file-width="2000" data-file-height="3008" /></a><figcaption><a href="/wiki/Boundary_marker" title="Boundary marker">Stone marking</a> the <a href="/wiki/Austria-Hungary" title="Austria-Hungary">Austro-Hungarian</a>/Italian border at <a href="/wiki/Pontebba" title="Pontebba">Pontebba</a> displaying <a href="/wiki/Myriametre" class="mw-redirect" title="Myriametre">myriametres</a>, a unit of 10 km used in <a href="/wiki/Central_Europe" title="Central Europe">Central Europe</a> in the 19th century (but since <a href="/wiki/Deprecation" title="Deprecation">deprecated</a>)<a href="#cite_note-Europa1842-36">[28]</a></figcaption></figure> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">For broader coverage of this topic, see <a href="/wiki/History_of_the_metric_system" title="History of the metric system">History of the metric system</a>.</div> <div class="mw-heading mw-heading3"><h3 id="CGS_and_MKS_systems">CGS and MKS systems</h3>[<a href="/w/index.php?title=International_System_of_Units&action=edit&section=15" title="Edit section: CGS and MKS systems">edit</a>]</div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">See also: <a href="/wiki/CGS_system_of_units" class="mw-redirect" title="CGS system of units">CGS system of units</a></div> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:US_National_Length_Meter.JPG" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/a/a5/US_National_Length_Meter.JPG/220px-US_National_Length_Meter.JPG" decoding="async" width="220" height="189" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/a/a5/US_National_Length_Meter.JPG/330px-US_National_Length_Meter.JPG 1.5x, //upload.wikimedia.org/wikipedia/commons/a/a5/US_National_Length_Meter.JPG 2x" data-file-width="350" data-file-height="300" /></a><figcaption>Closeup of the National Prototype Metre, serial number 27, allocated to the United States</figcaption></figure> The concept of a system of units emerged a hundred years before the SI. In the 1860s, <a href="/wiki/James_Clerk_Maxwell" title="James Clerk Maxwell">James Clerk Maxwell</a>, <a href="/wiki/William_Thomson,_1st_Baron_Kelvin" class="mw-redirect" title="William Thomson, 1st Baron Kelvin">William Thomson</a> (later Lord Kelvin), and others working under the auspices of the <a href="/wiki/British_Association_for_the_Advancement_of_Science" class="mw-redirect" title="British Association for the Advancement of Science">British Association for the Advancement of Science</a>, building on previous work of <a href="/wiki/Carl_Gauss" class="mw-redirect" title="Carl Gauss">Carl Gauss</a>, developed the <a href="/wiki/Centimetre%E2%80%93gram%E2%80%93second_system_of_units" title="Centimetre–gram–second system of units">centimetre–gram–second system of units</a> or cgs system in 1874. The systems formalised the concept of a collection of related units called a coherent system of units. In a coherent system, base units combine to define derived units without extra factors.<a href="#cite_note-NIST330-6">[4]</a>: 2  For example, using meters per second is coherent in a system that uses meter for length and seconds for time, but kilometre per hour is not coherent. The principle of coherence was successfully used to define a number of units of measure based on the CGS, including the <a href="/wiki/Erg" title="Erg">erg</a> for <a href="/wiki/Energy" title="Energy">energy</a>, the <a href="/wiki/Dyne" title="Dyne">dyne</a> for <a href="/wiki/Force" title="Force">force</a>, the <a href="/wiki/Barye" title="Barye">barye</a> for <a href="/wiki/Pressure" title="Pressure">pressure</a>, the <a href="/wiki/Poise_(unit)" title="Poise (unit)">poise</a> for <a href="/wiki/Dynamic_viscosity" class="mw-redirect" title="Dynamic viscosity">dynamic viscosity</a> and the <a href="/wiki/Stokes_(unit)" class="mw-redirect" title="Stokes (unit)">stokes</a> for <a href="/wiki/Kinematic_viscosity" class="mw-redirect" title="Kinematic viscosity">kinematic viscosity</a>.<a href="#cite_note-BIPMCentenary-37">[29]</a> <div class="mw-heading mw-heading3"><h3 id="Metre_Convention">Metre Convention</h3>[<a href="/w/index.php?title=International_System_of_Units&action=edit&section=16" title="Edit section: Metre Convention">edit</a>]</div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main articles: <a href="/wiki/Metre_Convention" title="Metre Convention">Metre Convention</a> and <a href="/wiki/MKS_system_of_units" class="mw-redirect" title="MKS system of units">MKS system of units</a></div> A French-inspired initiative for international cooperation in <a href="/wiki/Metrology" title="Metrology">metrology</a> led to the signing in 1875 of the <a href="/wiki/Metre_Convention" title="Metre Convention">Metre Convention</a>, also called Treaty of the Metre, by 17 nations.<a href="#cite_note-38">[e]</a><a href="#cite_note-Alder-39">[30]</a>: 353–354  The <a href="/wiki/General_Conference_on_Weights_and_Measures" title="General Conference on Weights and Measures">General Conference on Weights and Measures</a> (French: Conférence générale des poids et mesures – CGPM), which was established by the Metre Convention,<a href="#cite_note-BIPMCentenary-37">[29]</a> brought together many international organisations to establish the definitions and standards of a new system and to standardise the rules for writing and presenting measurements.<a href="#cite_note-Giunta-40">[31]</a>: 37 <a href="#cite_note-41">[32]</a> Initially the convention only covered standards for the metre and the kilogram. This became the foundation of the MKS system of units.<a href="#cite_note-NIST330-6">[4]</a>: 2  <div class="mw-heading mw-heading3"><h3 id="Giovanni_Giorgi_and_the_problem_of_electrical_units">Giovanni Giorgi and the problem of electrical units</h3>[<a href="/w/index.php?title=International_System_of_Units&action=edit&section=17" title="Edit section: Giovanni Giorgi and the problem of electrical units">edit</a>]</div> At the close of the 19th century three different systems of units of measure existed for electrical measurements: a <a href="/wiki/CGS-based_system_for_electrostatic_units" class="mw-redirect" title="CGS-based system for electrostatic units">CGS-based system for electrostatic units</a>, also known as the Gaussian or ESU system, a <a href="/wiki/CGS-based_system_for_electromechanical_units" class="mw-redirect" title="CGS-based system for electromechanical units">CGS-based system for electromechanical units</a> (EMU), and an International system based on units defined by the Metre Convention<a href="#cite_note-42">[33]</a> for electrical distribution systems. Attempts to resolve the electrical units in terms of length, mass, and time using <a href="/wiki/Dimensional_analysis" title="Dimensional analysis">dimensional analysis</a> was beset with difficulties – the dimensions depended on whether one used the ESU or EMU systems.<a href="#cite_note-Maxwell2-43">[34]</a> This anomaly was resolved in 1901 when <a href="/wiki/Giovanni_Giorgi" title="Giovanni Giorgi">Giovanni Giorgi</a> published a paper in which he advocated using a fourth base unit alongside the existing three base units. The fourth unit could be chosen to be <a href="/wiki/Electric_current" title="Electric current">electric current</a>, <a href="/wiki/Voltage" title="Voltage">voltage</a>, or <a href="/wiki/Electrical_resistance" class="mw-redirect" title="Electrical resistance">electrical resistance</a>.<a href="#cite_note-IECGiorgi-44">[35]</a> Electric current with named unit 'ampere' was chosen as the base unit, and the other electrical quantities derived from it according to the laws of physics. When combined with the MKS the new system, known as MKSA, was approved in 1946.<a href="#cite_note-NIST330-6">[4]</a> <div class="mw-heading mw-heading3"><h3 id="9th_CGPM,_the_precursor_to_SI">9th CGPM, the precursor to SI</h3>[<a href="/w/index.php?title=International_System_of_Units&action=edit&section=18" title="Edit section: 9th CGPM, the precursor to SI">edit</a>]</div> In 1948, the 9th CGPM commissioned a study to assess the measurement needs of the scientific, technical, and educational communities and "to make recommendations for a single practical system of units of measurement, suitable for adoption by all countries adhering to the Metre Convention".<a href="#cite_note-45">[36]</a> This working document was Practical system of units of measurement. Based on this study, the 10th CGPM in 1954 defined an international system derived six base units: the metre, kilogram, second, ampere, degree Kelvin, and candela. The 9th CGPM also approved the first formal recommendation for the writing of symbols in the metric system when the basis of the rules as they are now known was laid down.<a href="#cite_note-46">[37]</a> These rules were subsequently extended and now cover unit symbols and names, prefix symbols and names, how quantity symbols should be written and used, and how the values of quantities should be expressed.<a href="#cite_note-SIBrochure-8">[5]</a>: 104, 130  <div class="mw-heading mw-heading3"><h3 id="Birth_of_the_SI">Birth of the SI</h3>[<a href="/w/index.php?title=International_System_of_Units&action=edit&section=19" title="Edit section: Birth of the SI">edit</a>]</div> The 10th CGPM in 1954 resolved to create an international system of units<a href="#cite_note-Giunta-40">[31]</a>: 41  and in 1960, the 11th CGPM adopted the International System of Units, abbreviated SI from the French name Le Système international d'unités, which included a specification for units of measurement.<a href="#cite_note-SIBrochure-8">[5]</a>: 110  The <a href="/wiki/International_Bureau_of_Weights_and_Measures" title="International Bureau of Weights and Measures">International Bureau of Weights and Measures</a> (BIPM) has described SI as "the modern form of metric system".<a href="#cite_note-SIBrochure-8">[5]</a>: 95  In 1971 the <a href="/wiki/Mole_(unit)" title="Mole (unit)">mole</a> became the seventh base unit of the SI.<a href="#cite_note-NIST330-6">[4]</a>: 2  <div class="mw-heading mw-heading3"><h3 id="2019_redefinition">2019 redefinition</h3>[<a href="/w/index.php?title=International_System_of_Units&action=edit&section=20" title="Edit section: 2019 redefinition">edit</a>]</div> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Unit_relations_in_the_new_SI.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/a/ab/Unit_relations_in_the_new_SI.svg/220px-Unit_relations_in_the_new_SI.svg.png" decoding="async" width="220" height="211" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/a/ab/Unit_relations_in_the_new_SI.svg/330px-Unit_relations_in_the_new_SI.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/a/ab/Unit_relations_in_the_new_SI.svg/440px-Unit_relations_in_the_new_SI.svg.png 2x" data-file-width="625" data-file-height="600" /></a><figcaption>Reverse dependencies of the SI base units on seven <a href="/wiki/Physical_constant" title="Physical constant">physical constants</a>, which are assigned exact numerical values in the <a href="/wiki/2019_revision_of_the_SI" title="2019 revision of the SI">2019 redefinition</a>. Unlike in the previous definitions, the base units are all derived exclusively from constants of nature. Here, <math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle a\rightarrow b}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>a</mi> <mo stretchy="false">→</mo> <mi>b</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle a\rightarrow b}</annotation> </semantics> </math><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/390afdb0d8e933dbc4eee8022d8c91b2015f0522" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:5.841ex; height:2.176ex;" alt="{\displaystyle a\rightarrow b}"> means that <math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle a}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>a</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle a}</annotation> </semantics> </math><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/ffd2487510aa438433a2579450ab2b3d557e5edc" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.23ex; height:1.676ex;" alt="{\displaystyle a}"> is used to define <math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle b}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>b</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle b}</annotation> </semantics> </math><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/f11423fbb2e967f986e36804a8ae4271734917c3" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:0.998ex; height:2.176ex;" alt="{\displaystyle b}">.</figcaption></figure> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/2019_revision_of_the_SI" title="2019 revision of the SI">2019 revision of the SI</a></div> After the <a href="/wiki/History_of_the_metre" title="History of the metre">metre was redefined</a> in 1960, the <a href="/wiki/International_Prototype_of_the_Kilogram" title="International Prototype of the Kilogram">International Prototype of the Kilogram</a> (IPK) was the only physical artefact upon which base units (directly the kilogram and indirectly the ampere, mole and candela) depended for their definition, making these units subject to periodic comparisons of national standard kilograms with the IPK.<a href="#cite_note-NPL_kg-47">[38]</a> During the 2nd and 3rd Periodic Verification of National Prototypes of the Kilogram, a significant divergence had occurred between the mass of the IPK and all of its official copies stored around the world: the copies had all noticeably increased in mass with respect to the IPK. During extraordinary verifications carried out in 2014 preparatory to redefinition of metric standards, continuing divergence was not confirmed. Nonetheless, the residual and irreducible instability of a physical IPK undermined the reliability of the entire metric system to precision measurement from small (atomic) to large (astrophysical) scales.<a href="#cite_note-48">[39]</a> By avoiding the use of an artefact to define units, all issues with the loss, damage, and change of the artefact are avoided.<a href="#cite_note-SIBrochure9thEd-1">[1]</a>: 125  A proposal was made that:<a href="#cite_note-49">[40]</a> <ul><li>In addition to the speed of light, four constants of nature – the <a href="/wiki/Planck_constant" title="Planck constant">Planck constant</a>, an <a href="/wiki/Elementary_charge" title="Elementary charge">elementary charge</a>, the <a href="/wiki/Boltzmann_constant" title="Boltzmann constant">Boltzmann constant</a>, and the <a href="/wiki/Avogadro_constant" title="Avogadro constant">Avogadro constant</a> – be defined to have exact values</li> <li>The <a href="/wiki/International_Prototype_of_the_Kilogram" title="International Prototype of the Kilogram">International Prototype of the Kilogram</a> be retired</li> <li>The current definitions of the kilogram, ampere, kelvin, and mole be revised</li> <li>The wording of base unit definitions should change emphasis from explicit unit to explicit constant definitions.</li></ul> The new definitions were adopted at the 26th CGPM on 16 November 2018, and came into effect on 20 May 2019.<a href="#cite_note-50">[41]</a> The change was adopted by the European Union through Directive (EU) 2019/1258.<a href="#cite_note-51">[42]</a> Prior to its redefinition in 2019, the SI was defined through the seven base units from which the derived units were constructed as products of powers of the base units. After the redefinition, the SI is defined by fixing the numerical values of seven defining constants. This has the effect that the distinction between the base units and derived units is, in principle, not needed, since all units, base as well as derived, may be constructed directly from the defining constants. Nevertheless, the distinction is retained because "it is useful and historically well established", and also because the <a href="/wiki/ISO/IEC_80000" title="ISO/IEC 80000">ISO/IEC 80000</a> series of standards, which define the <a href="/wiki/International_System_of_Quantities" title="International System of Quantities">International System of Quantities</a> (ISQ), specifies base and derived quantities that necessarily have the corresponding SI units.<a href="#cite_note-SIBrochure9thEd-1">[1]</a>: 129  <div class="mw-heading mw-heading2"><h2 id="Related_units">Related units</h2>[<a href="/w/index.php?title=International_System_of_Units&action=edit&section=21" title="Edit section: Related units">edit</a>]</div> <div class="mw-heading mw-heading3"><h3 id="Non-SI_units_accepted_for_use_with_SI">Non-SI units accepted for use with SI</h3>[<a href="/w/index.php?title=International_System_of_Units&action=edit&section=22" title="Edit section: Non-SI units accepted for use with SI">edit</a>]</div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Non-SI_units_mentioned_in_the_SI" title="Non-SI units mentioned in the SI">Non-SI units mentioned in the SI</a></div> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:CubeLitre.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/b/b9/CubeLitre.svg/240px-CubeLitre.svg.png" decoding="async" width="240" height="192" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/b9/CubeLitre.svg/360px-CubeLitre.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/b9/CubeLitre.svg/480px-CubeLitre.svg.png 2x" data-file-width="385" data-file-height="308" /></a><figcaption>While not an SI-unit, the litre may be used with SI units. It is equivalent to (10 cm)3 = (1 dm)3 = 10−3 m3.</figcaption></figure> Many non-SI units continue to be used in the scientific, technical, and commercial literature. Some units are deeply embedded in history and culture, and their use has not been entirely replaced by their SI alternatives. The CIPM recognised and acknowledged such traditions by compiling a list of <a href="/wiki/Non-SI_units_mentioned_in_the_SI" title="Non-SI units mentioned in the SI">non-SI units accepted for use with SI</a>,<a href="#cite_note-SIBrochure-8">[5]</a> including the hour, minute, degree of angle, litre, and decibel. <div class="mw-heading mw-heading3"><h3 id="Metric_units_not_recognised_by_SI">Metric units not recognised by SI</h3>[<a href="/w/index.php?title=International_System_of_Units&action=edit&section=23" title="Edit section: Metric units not recognised by SI">edit</a>]</div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/List_of_metric_units" title="List of metric units">List of metric units</a></div> Although the term metric system is often used as an informal alternative name for the International System of Units,<a href="#cite_note-MetricSystemAsNameForSI-52">[43]</a> other metric systems exist, some of which were in widespread use in the past or are even still used in particular areas. There are also individual <a href="/wiki/Metric_units" class="mw-redirect" title="Metric units">metric units</a> such as the <a href="/wiki/Sverdrup" title="Sverdrup">sverdrup</a> and the <a href="/wiki/Darcy_(unit)" title="Darcy (unit)">darcy</a> that exist outside of any system of units. Most of the units of the other metric systems are not recognised by the SI. <div class="mw-heading mw-heading3"><h3 id="Unacceptable_uses">Unacceptable uses</h3>[<a href="/w/index.php?title=International_System_of_Units&action=edit&section=24" title="Edit section: Unacceptable uses">edit</a>]</div> Sometimes, SI unit name variations are introduced, mixing information about the corresponding physical quantity or the conditions of its measurement; however, this practice is unacceptable with the SI. "Unacceptability of mixing information with units: When one gives the value of a quantity, any information concerning the quantity or its conditions of measurement must be presented in such a way as not to be associated with the unit."<a href="#cite_note-SIBrochure-8">[5]</a> Instances include: "<a href="/wiki/Watt-peak" class="mw-redirect" title="Watt-peak">watt-peak</a>" and "<a href="/wiki/Watt_RMS" class="mw-redirect" title="Watt RMS">watt RMS</a>"; "<a href="/wiki/Geopotential_metre" class="mw-redirect" title="Geopotential metre">geopotential metre</a>" and "<a href="/wiki/Vertical_metre" class="mw-redirect" title="Vertical metre">vertical metre</a>"; "<a href="/wiki/Standard_cubic_metre" class="mw-redirect" title="Standard cubic metre">standard cubic metre</a>"; "<a href="/wiki/Atomic_second" class="mw-redirect" title="Atomic second">atomic second</a>", "<a href="/wiki/Ephemeris_second" class="mw-redirect" title="Ephemeris second">ephemeris second</a>", and "<a href="/wiki/Sidereal_second" class="mw-redirect" title="Sidereal second">sidereal second</a>". <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2>[<a href="/w/index.php?title=International_System_of_Units&action=edit&section=25" title="Edit section: See also">edit</a>]</div> <style data-mw-deduplicate="TemplateStyles:r1184024115">.mw-parser-output .div-col{margin-top:0.3em;column-width:30em}.mw-parser-output .div-col-small{font-size:90%}.mw-parser-output .div-col-rules{column-rule:1px solid #aaa}.mw-parser-output .div-col dl,.mw-parser-output .div-col ol,.mw-parser-output .div-col ul{margin-top:0}.mw-parser-output .div-col li,.mw-parser-output .div-col dd{page-break-inside:avoid;break-inside:avoid-column}</style><div class="div-col" style="column-width: 30em;"> <ul><li><a href="/wiki/Conversion_of_units" title="Conversion of units">Conversion of units</a> – Comparison of various scales</li> <li><a href="/wiki/List_of_international_common_standards" title="List of international common standards">List of international common standards</a></li> <li><a href="/wiki/Metrication" title="Metrication">Metrication</a></li> <li><a href="/wiki/Outline_of_the_metric_system" title="Outline of the metric system">Outline of the metric system</a> – Overview of and topical guide to the metric system</li></ul> Organisations <ul><li><a href="/wiki/International_Bureau_of_Weights_and_Measures" title="International Bureau of Weights and Measures">International Bureau of Weights and Measures</a> – Intergovernmental measurement science and measurement standards setting organisation</li> <li><a href="/wiki/Institute_for_Reference_Materials_and_Measurements" title="Institute for Reference Materials and Measurements">Institute for Reference Materials and Measurements</a> – research organization for a common European measurement systemPages displaying wikidata descriptions as a fallback (EU)</li> <li><a href="/wiki/National_Institute_of_Standards_and_Technology" title="National Institute of Standards and Technology">National Institute of Standards and Technology</a> – Measurement standards laboratory in the United States (US)</li></ul> Standards and conventions <ul><li><a href="/wiki/Conventional_electrical_unit" title="Conventional electrical unit">Conventional electrical unit</a> – Historical high-precision units of measurement</li> <li><a href="/wiki/Coordinated_Universal_Time" title="Coordinated Universal Time">Coordinated Universal Time</a> (<abbr>UTC</abbr>) – Primary time standard</li> <li><a href="/wiki/Unified_Code_for_Units_of_Measure" title="Unified Code for Units of Measure">Unified Code for Units of Measure</a> – System of codes for unambiguously representing measurement units</li></ul></div> <div class="mw-heading mw-heading2"><h2 id="Notes">Notes</h2>[<a href="/w/index.php?title=International_System_of_Units&action=edit&section=26" title="Edit section: Notes">edit</a>]</div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239543626"><div class="reflist reflist-lower-alpha"> <div class="mw-references-wrap"><ol class="references"> <li id="cite_note-9"><a href="#cite_ref-9">^</a> Ohm's law: 1 Ω = 1 V/A from the relationship E = I × R, where E is electromotive force or voltage (unit: volt), I is current (unit: ampere), and R is resistance (unit: ohm). </li> <li id="cite_note-French_CGPM-31"><a href="#cite_ref-French_CGPM_31-0">^</a> From <a href="/wiki/French_language" title="French language">French</a>: Conférence générale des poids et mesures. </li> <li id="cite_note-French_CIPM-33"><a href="#cite_ref-French_CIPM_33-0">^</a> from <a href="/wiki/French_language" title="French language">French</a>: Comité international des poids et mesures </li> <li id="cite_note-BIPM_from_French-34"><a href="#cite_ref-BIPM_from_French_34-0">^</a> from <a href="/wiki/French_language" title="French language">French</a>: Bureau international des poids et mesures </li> <li id="cite_note-38"><a href="#cite_ref-38">^</a> Argentina, Austria-Hungary, Belgium, Brazil, Denmark, France, German Empire, Italy, Peru, Portugal, Russia, Spain, Sweden and Norway, Switzerland, Ottoman Empire, United States, and Venezuela. </li> </ol></div></div> <dl><dt>Attribution</dt></dl> <a href="#cite_note-SIBrochure9thEd-1">[1]</a><a href="//creativecommons.org/licenses/by/3.0/" title="creativecommons:by/3.0/"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/6/65/Creative_Commons_by_small.svg/80px-Creative_Commons_by_small.svg.png" decoding="async" width="80" height="15" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/6/65/Creative_Commons_by_small.svg/120px-Creative_Commons_by_small.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/6/65/Creative_Commons_by_small.svg/160px-Creative_Commons_by_small.svg.png 2x" data-file-width="80" data-file-height="15" /></a> This article incorporates <a rel="nofollow" class="external text" href="https://www.bipm.org/documents/20126/41483022/SI-Brochure-9-EN.pdf">text</a> from this source, which is available under the <a href="//creativecommons.org/licenses/by/3.0/" class="extiw" title="creativecommons:by/3.0/">CC BY 3.0</a> license. <div class="mw-heading mw-heading2"><h2 id="References">References</h2>[<a href="/w/index.php?title=International_System_of_Units&action=edit&section=27" title="Edit section: References">edit</a>]</div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239543626"><div class="reflist"> <div class="mw-references-wrap mw-references-columns"><ol class="references"> <li id="cite_note-SIBrochure9thEd-1">^ <a href="#cite_ref-SIBrochure9thEd_1-0">a</a> <a href="#cite_ref-SIBrochure9thEd_1-1">b</a> <a href="#cite_ref-SIBrochure9thEd_1-2">c</a> <a href="#cite_ref-SIBrochure9thEd_1-3">d</a> <a href="#cite_ref-SIBrochure9thEd_1-4">e</a> <a href="#cite_ref-SIBrochure9thEd_1-5">f</a> <a href="#cite_ref-SIBrochure9thEd_1-6">g</a> <a href="#cite_ref-SIBrochure9thEd_1-7">h</a> <a href="#cite_ref-SIBrochure9thEd_1-8">i</a> <a href="#cite_ref-SIBrochure9thEd_1-9">j</a> <a href="#cite_ref-SIBrochure9thEd_1-10">k</a> <a href="#cite_ref-SIBrochure9thEd_1-11">l</a> <a href="#cite_ref-SIBrochure9thEd_1-12">m</a> <a href="#cite_ref-SIBrochure9thEd_1-13">n</a> <a href="#cite_ref-SIBrochure9thEd_1-14">o</a> <a href="#cite_ref-SIBrochure9thEd_1-15">p</a> <a href="#cite_ref-SIBrochure9thEd_1-16">q</a> <a href="#cite_ref-SIBrochure9thEd_1-17">r</a> <a href="#cite_ref-SIBrochure9thEd_1-18">s</a> <a href="#cite_ref-SIBrochure9thEd_1-19">t</a> <a href="#cite_ref-SIBrochure9thEd_1-20">u</a> <a href="#cite_ref-SIBrochure9thEd_1-21">v</a> <a href="#cite_ref-SIBrochure9thEd_1-22">w</a> <a href="#cite_ref-SIBrochure9thEd_1-23">x</a> <a href="#cite_ref-SIBrochure9thEd_1-24">y</a> <a href="#cite_ref-SIBrochure9thEd_1-25">z</a> <a href="#cite_ref-SIBrochure9thEd_1-26">aa</a> <a href="#cite_ref-SIBrochure9thEd_1-27">ab</a> <a href="#cite_ref-SIBrochure9thEd_1-28">ac</a> <a href="#cite_ref-SIBrochure9thEd_1-29">ad</a> <style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon 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Retrieved 27 April 2021.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Appendix+1.+Decisions+of+the+CGPM+and+the+CIPM&rft.pages=188&rft.pub=BIPM&rft_id=https%3A%2F%2Fwww.bipm.org%2Fdocuments%2F20126%2F41483022%2FSI-Brochure-9-App4-EN.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AInternational+System+of+Units" class="Z3988"> </li> <li id="cite_note-50"><a href="#cite_ref-50">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFWood2014" class="citation web cs1">Wood, B. (3–4 November 2014). <a rel="nofollow" class="external text" href="http://www.bipm.org/cc/TGFC/Allowed/Minutes/CODATA_Minutes_14-BIPM-public.pdf">"Report on the Meeting of the CODATA Task Group on Fundamental Constants"</a> (PDF). <a href="/wiki/BIPM" class="mw-redirect" title="BIPM">BIPM</a>. p. 7. <q>[BIPM director Martin] Milton responded to a question about what would happen if ... the CIPM or the CGPM voted not to move forward with the redefinition of the SI. He responded that he felt that by that time the decision to move forward should be seen as a foregone conclusion.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Report+on+the+Meeting+of+the+CODATA+Task+Group+on+Fundamental+Constants&rft.pages=7&rft.pub=BIPM&rft.date=2014-11-03%2F2014-11-04&rft.aulast=Wood&rft.aufirst=B.&rft_id=http%3A%2F%2Fwww.bipm.org%2Fcc%2FTGFC%2FAllowed%2FMinutes%2FCODATA_Minutes_14-BIPM-public.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AInternational+System+of+Units" class="Z3988"> </li> <li id="cite_note-51"><a href="#cite_ref-51">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://eur-lex.europa.eu/eli/dir/2019/1258/oj">"Commission Directive (EU) 2019/1258 of 23 July 2019 amending, for the purpose of its adaptation to technical progress, the Annex to Council Directive 80/181/EEC as regards the definitions of SI base units"</a>. <a href="/wiki/Eur-Lex" class="mw-redirect" title="Eur-Lex">Eur-Lex</a>. 23 July 2019. Retrieved 28 August 2019.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Eur-Lex&rft.atitle=Commission+Directive+%28EU%29+2019%2F1258+of+23+July+2019+amending%2C+for+the+purpose+of+its+adaptation+to+technical+progress%2C+the+Annex+to+Council+Directive+80%2F181%2FEEC+as+regards+the+definitions+of+SI+base+units&rft.date=2019-07-23&rft_id=https%3A%2F%2Feur-lex.europa.eu%2Feli%2Fdir%2F2019%2F1258%2Foj&rfr_id=info%3Asid%2Fen.wikipedia.org%3AInternational+System+of+Units" class="Z3988"> </li> <li id="cite_note-MetricSystemAsNameForSI-52"><a href="#cite_ref-MetricSystemAsNameForSI_52-0">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFOlthoff2018" class="citation journal cs1">Olthoff, Jim (2018). <a rel="nofollow" class="external text" href="https://www.nist.gov/blogs/taking-measure/all-times-all-peoples-how-replacing-kilogram-empowers-industry">"For All Times, For All Peoples: How Replacing the Kilogram Empowers Industry"</a>. <a href="/wiki/NIST" class="mw-redirect" title="NIST">NIST</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20200316195625/https://www.nist.gov/blogs/taking-measure/all-times-all-peoples-how-replacing-kilogram-empowers-industry">Archived</a> from the original on 16 March 2020. Retrieved 14 April 2020. <q>... the International System of Units (SI), popularly known as the metric system.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=NIST&rft.atitle=For+All+Times%2C+For+All+Peoples%3A+How+Replacing+the+Kilogram+Empowers+Industry&rft.date=2018&rft.aulast=Olthoff&rft.aufirst=Jim&rft_id=https%3A%2F%2Fwww.nist.gov%2Fblogs%2Ftaking-measure%2Fall-times-all-peoples-how-replacing-kilogram-empowers-industry&rfr_id=info%3Asid%2Fen.wikipedia.org%3AInternational+System+of+Units" class="Z3988"> </li> </ol></div></div> <div class="mw-heading mw-heading2"><h2 id="Further_reading">Further reading</h2>[<a href="/w/index.php?title=International_System_of_Units&action=edit&section=28" title="Edit section: Further reading">edit</a>]</div> <style data-mw-deduplicate="TemplateStyles:r1239549316">.mw-parser-output .refbegin{margin-bottom:0.5em}.mw-parser-output .refbegin-hanging-indents>ul{margin-left:0}.mw-parser-output .refbegin-hanging-indents>ul>li{margin-left:0;padding-left:3.2em;text-indent:-3.2em}.mw-parser-output .refbegin-hanging-indents ul,.mw-parser-output .refbegin-hanging-indents ul li{list-style:none}@media(max-width:720px){.mw-parser-output .refbegin-hanging-indents>ul>li{padding-left:1.6em;text-indent:-1.6em}}.mw-parser-output .refbegin-columns{margin-top:0.3em}.mw-parser-output .refbegin-columns ul{margin-top:0}.mw-parser-output .refbegin-columns li{page-break-inside:avoid;break-inside:avoid-column}@media screen{.mw-parser-output .refbegin{font-size:90%}}</style><div class="refbegin" style=""> <ul><li><a href="/wiki/International_Union_of_Pure_and_Applied_Chemistry" title="International Union of Pure and Applied Chemistry">International Union of Pure and Applied Chemistry</a> (1993). <a href="/wiki/Quantities,_Units_and_Symbols_in_Physical_Chemistry" title="Quantities, Units and Symbols in Physical Chemistry">Quantities, Units and Symbols in Physical Chemistry</a>, 2nd edition, Oxford: Blackwell Science. <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-632-03583-8" title="Special:BookSources/0-632-03583-8">0-632-03583-8</a>. <a rel="nofollow" class="external text" href="https://old.iupac.org/publications/books/gbook/green_book_2ed.pdf">Electronic version.</a></li> <li><a rel="nofollow" class="external text" href="http://info.ee.surrey.ac.uk/Workshop/advice/coils/unit_systems/#rms">Unit Systems in Electromagnetism</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20201030081637/http://info.ee.surrey.ac.uk/Workshop/advice/coils/unit_systems/#rms">Archived</a> 30 October 2020 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a></li> <li><a rel="nofollow" class="external text" href="https://www.nist.gov/customcf/get_pdf.cfm?pub_id=32943">MW Keller et al.</a> (PDF) Metrology Triangle Using a Watt Balance, a Calculable Capacitor, and a Single-Electron Tunnelling Device</li> <li><a rel="nofollow" class="external text" href="http://nvlpubs.nist.gov/nistpubs/jres/116/6/V116.N06.A01.pdf">"The Current SI Seen From the Perspective of the Proposed New SI"</a> (PDF). Barry N. Taylor. Journal of Research of the National Institute of Standards and Technology, Vol. 116, No. 6, Pgs. 797–807, Nov–Dec 2011.</li> <li>B. N. Taylor, Ambler Thompson, International System of Units (SI), <a href="/wiki/National_Institute_of_Standards_and_Technology" title="National Institute of Standards and Technology">National Institute of Standards and Technology</a> 2008 edition, <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/1437915582" title="Special:BookSources/1437915582">1437915582</a>.</li></ul> </div> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2>[<a href="/w/index.php?title=International_System_of_Units&action=edit&section=29" title="Edit section: External links">edit</a>]</div> <style data-mw-deduplicate="TemplateStyles:r1235681985">.mw-parser-output .side-box{margin:4px 0;box-sizing:border-box;border:1px solid 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href="/wiki/SI_base_unit" title="SI base unit">Base units</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Ampere" title="Ampere">ampere</a></li> <li><a href="/wiki/Candela" title="Candela">candela</a></li> <li><a href="/wiki/Kelvin" title="Kelvin">kelvin</a></li> <li><a href="/wiki/Kilogram" title="Kilogram">kilogram</a></li> <li><a href="/wiki/Metre" title="Metre">metre</a></li> <li><a href="/wiki/Mole_(unit)" title="Mole (unit)">mole</a></li> <li><a href="/wiki/Second" title="Second">second</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/SI_derived_unit" title="SI derived unit">Derived units with special names</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Becquerel" title="Becquerel">becquerel</a></li> <li><a href="/wiki/Coulomb" title="Coulomb">coulomb</a></li> <li><a href="/wiki/Celsius" title="Celsius">degree Celsius</a></li> <li><a href="/wiki/Farad" title="Farad">farad</a></li> <li><a href="/wiki/Gray_(unit)" title="Gray (unit)">gray</a></li> <li><a href="/wiki/Henry_(unit)" title="Henry (unit)">henry</a></li> <li><a href="/wiki/Hertz" title="Hertz">hertz</a></li> <li><a href="/wiki/Joule" title="Joule">joule</a></li> <li><a href="/wiki/Katal" title="Katal">katal</a></li> <li><a href="/wiki/Lumen_(unit)" title="Lumen (unit)">lumen</a></li> <li><a href="/wiki/Lux" title="Lux">lux</a></li> <li><a href="/wiki/Newton_(unit)" title="Newton (unit)">newton</a></li> <li><a href="/wiki/Ohm" title="Ohm">ohm</a></li> <li><a href="/wiki/Pascal_(unit)" title="Pascal (unit)">pascal</a></li> <li><a href="/wiki/Radian" title="Radian">radian</a></li> <li><a href="/wiki/Siemens_(unit)" title="Siemens (unit)">siemens</a></li> <li><a href="/wiki/Sievert" title="Sievert">sievert</a></li> <li><a href="/wiki/Steradian" title="Steradian">steradian</a></li> <li><a href="/wiki/Tesla_(unit)" title="Tesla (unit)">tesla</a></li> <li><a href="/wiki/Volt" title="Volt">volt</a></li> <li><a href="/wiki/Watt" title="Watt">watt</a></li> <li><a href="/wiki/Weber_(unit)" title="Weber (unit)">weber</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Non-SI_units_mentioned_in_the_SI" title="Non-SI units mentioned in the SI">Other accepted units</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Astronomical_unit" title="Astronomical unit">astronomical unit</a></li> <li><a href="/wiki/Dalton_(unit)" title="Dalton (unit)">dalton</a></li> <li><a href="/wiki/Day" title="Day">day</a></li> <li><a href="/wiki/Decibel" title="Decibel">decibel</a></li> <li><a href="/wiki/Degree_(angle)" title="Degree (angle)">degree of arc</a></li> <li><a href="/wiki/Electronvolt" title="Electronvolt">electronvolt</a></li> <li><a href="/wiki/Hectare" title="Hectare">hectare</a></li> <li><a href="/wiki/Hour" title="Hour">hour</a></li> <li><a href="/wiki/Litre" title="Litre">litre</a></li> <li><a href="/wiki/Minute" title="Minute">minute</a></li> <li><a href="/wiki/Minute_and_second_of_arc" title="Minute and second of arc">minute and second of arc</a></li> <li><a href="/wiki/Neper" title="Neper">neper</a></li> <li><a href="/wiki/Tonne" title="Tonne">tonne</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">See also</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Conversion_of_units" title="Conversion of units">Conversion of units</a></li> <li><a href="/wiki/Metric_prefix" title="Metric prefix">Metric prefixes</a></li> <li><a href="/wiki/Historical_definitions_of_the_SI_base_units" title="Historical definitions of the SI base units">Historical definitions of the SI base units</a></li> <li><a href="/wiki/2019_revision_of_the_SI" title="2019 revision of the SI">2019 revision of the SI</a></li> <li><a href="/wiki/System_of_units_of_measurement" title="System of units of measurement">System of units of measurement</a></li></ul> </div></td></tr><tr><td class="navbox-abovebelow" colspan="2"><div> <ul><li><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/16px-Symbol_category_class.svg.png" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/23px-Symbol_category_class.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/31px-Symbol_category_class.svg.png 2x" data-file-width="180" data-file-height="185" /> <a href="/wiki/Category:SI_units" title="Category:SI units">Category</a></li></ul> </div></td></tr></tbody></table></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236075235"></div><div role="navigation" class="navbox" aria-labelledby="Systems_of_measurement" style="padding:3px"><table class="nowraplinks mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="2"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239400231"><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Systems_of_measurement" title="Template:Systems of measurement"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Systems_of_measurement" title="Template talk:Systems of measurement"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Systems_of_measurement" title="Special:EditPage/Template:Systems of measurement"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Systems_of_measurement" style="font-size:114%;margin:0 4em"><a href="/wiki/System_of_measurement" class="mw-redirect" title="System of measurement">Systems of measurement</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">Current</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:5em">General</th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a class="mw-selflink selflink">International System of Units (SI)</a></li> <li><a href="/wiki/Imperial_units" title="Imperial units">UK imperial system</a></li> <li><a href="/wiki/United_States_customary_units" title="United States customary units">US customary units (USCS/USC)</a></li> <li><a href="/wiki/Chinese_units_of_measurement" title="Chinese units of measurement">Chinese</a> <ul><li><a href="/wiki/Hong_Kong_units_of_measurement" title="Hong Kong units of measurement">Hong Kong</a></li></ul></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:5em">Specific</th><td class="navbox-list-with-group navbox-list navbox-even" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Apothecaries%27_system" title="Apothecaries' system">Apothecaries'</a></li> <li><a href="/wiki/Avoirdupois_system" class="mw-redirect" title="Avoirdupois system">Avoirdupois</a></li> <li><a href="/wiki/Troy_weight" title="Troy weight">Troy</a></li> <li><a href="/wiki/Astronomical_system_of_units" title="Astronomical system of units">Astronomical</a></li> <li><a href="/wiki/Conventional_electrical_unit" title="Conventional electrical unit">Electrical</a></li> <li><a href="/wiki/English_Engineering_Units" title="English Engineering Units">English Engineering Units</a> (US)</li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:5em"><a href="/wiki/Natural_units" title="Natural units">Natural</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Atomic_units" title="Atomic units">Atomic</a></li> <li><a href="/wiki/Geometrized_unit_system" title="Geometrized unit system">Geometrised</a></li> <li><a href="/wiki/Heaviside%E2%80%93Lorentz_units" title="Heaviside–Lorentz units">Heaviside–Lorentz</a></li> <li><a href="/wiki/Planck_units" title="Planck units">Planck</a></li> <li><a href="/wiki/Natural_units#Quantum_chromodynamics_units" title="Natural units">Quantum chromodynamical</a></li> <li><a href="/wiki/Stoney_units" title="Stoney units">Stoney</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Background</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:5em">Metric</th><td class="navbox-list-with-group navbox-list navbox-even" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Metric_system" title="Metric system">Overview</a></li> <li><a href="/wiki/Outline_of_the_metric_system" title="Outline of the metric system">Outline</a></li> <li><a href="/wiki/History_of_the_metric_system" title="History of the metric system">History</a></li> <li><a href="/wiki/Metrication" title="Metrication">Metrication</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:5em">UK/US</th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Imperial_and_US_customary_measurement_systems" title="Imperial and US customary measurement systems">Overview</a></li> <li><a href="/wiki/Comparison_of_the_imperial_and_US_customary_measurement_systems" title="Comparison of the imperial and US customary measurement systems">Comparison</a></li> <li><a href="/wiki/Foot%E2%80%93pound%E2%80%93second_system" class="mw-redirect" title="Foot–pound–second system">Foot–pound–second</a> (FPS)</li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Historic</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:5em">Metric</th><td class="navbox-list-with-group navbox-list navbox-even" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/MKS_system_of_units" class="mw-redirect" title="MKS system of units">metre–kilogram–second</a> (MKS)</li> <li><a href="/wiki/Metre%E2%80%93tonne%E2%80%93second_system_of_units" title="Metre–tonne–second system of units">metre–tonne–second</a> (MTS)</li> <li><a href="/wiki/Centimetre%E2%80%93gram%E2%80%93second_system_of_units" title="Centimetre–gram–second system of units">centimetre–gram–second</a> (CGS)</li> <li><a href="/wiki/Gravitational_metric_system" title="Gravitational metric system">gravitational</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:5em">Europe</th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Old_Cornish_units_of_measurement" title="Old Cornish units of measurement">Cornish</a></li> <li><a href="/wiki/Cypriot_units_of_measurement" title="Cypriot units of measurement">Cypriot</a></li> <li><a href="/wiki/Czech_units_of_measurement" title="Czech units of measurement">Czech</a></li> <li><a href="/wiki/Danish_units_of_measurement" title="Danish units of measurement">Danish</a></li> <li><a href="/wiki/Dutch_units_of_measurement" title="Dutch units of measurement">Dutch</a></li> <li><a href="/wiki/English_units" title="English units">English</a> <ul><li><a href="/wiki/Winchester_measure" title="Winchester measure">Winchester</a></li> <li><a href="/wiki/Exchequer_Standards" title="Exchequer Standards">Exchequer</a></li></ul></li> <li><a href="/wiki/Estonian_units_of_measurement" title="Estonian units of measurement">Estonian</a></li> <li><a href="/wiki/Obsolete_Finnish_units_of_measurement" title="Obsolete Finnish units of measurement">Finnish</a></li> <li><a href="/wiki/French_units_of_measurement" title="French units of measurement">French</a> <ul><li><a href="/wiki/Traditional_French_units_of_measurement" title="Traditional French units of measurement">Traditional</a></li> <li><a href="/wiki/Mesures_usuelles" title="Mesures usuelles">Mesures usuelles</a></li></ul></li> <li><a href="/wiki/Obsolete_German_units_of_measurement" class="mw-redirect" title="Obsolete German units of measurement">German</a></li> <li><a href="/wiki/Greek_units_of_measurement" title="Greek units of measurement">Greek</a> <ul><li><a href="/wiki/Byzantine_units_of_measurement" title="Byzantine units of measurement">Byzantine</a></li></ul></li> <li><a href="/wiki/Hungarian_units_of_measurement" title="Hungarian units of measurement">Hungarian</a></li> <li><a href="/wiki/Icelandic_units_of_measurement" title="Icelandic units of measurement">Icelandic</a></li> <li><a href="/wiki/Old_Irish_units_of_measurement" class="mw-redirect" title="Old Irish units of measurement">Irish</a></li> <li><a href="/wiki/Italian_units_of_measurement" title="Italian units of measurement">Italian</a></li> <li><a href="/wiki/Latvian_units_of_measurement" title="Latvian units of measurement">Latvian</a></li> <li><a href="/wiki/Luxembourgian_units_of_measurement" class="mw-redirect" title="Luxembourgian units of measurement">Luxembourgian</a></li> <li><a href="/wiki/Maltese_units_of_measurement" title="Maltese units of measurement">Maltese</a></li> <li><a href="/wiki/Norwegian_units_of_measurement" title="Norwegian units of measurement">Norwegian</a></li> <li><a href="/wiki/Ottoman_units_of_measurement" title="Ottoman units of measurement">Ottoman</a></li> <li><a href="/wiki/Polish_units_of_measurement" title="Polish units of measurement">Polish</a></li> <li><a href="/wiki/Portuguese_units_of_measurement" title="Portuguese units of measurement">Portuguese</a></li> <li><a href="/wiki/Romanian_units_of_measurement" title="Romanian units of measurement">Romanian</a></li> <li><a href="/wiki/Obsolete_Russian_units_of_measurement" class="mw-redirect" title="Obsolete Russian units of measurement">Russian</a></li> <li><a href="/wiki/Scottish_units" title="Scottish units">Scottish</a></li> <li><a href="/wiki/Obsolete_Serbian_units_of_measurement" title="Obsolete Serbian units of measurement">Serbian</a></li> <li><a href="/wiki/Slovak_units_of_measurement" title="Slovak units of measurement">Slovak</a></li> <li><a href="/wiki/Spanish_units_of_measurement" title="Spanish units of measurement">Spanish</a></li> <li><a href="/wiki/Swedish_units_of_measurement" title="Swedish units of measurement">Swedish</a></li> <li><a href="/wiki/Swiss_units_of_measurement" title="Swiss units of measurement">Swiss</a></li> <li><a href="/wiki/Welsh_units" title="Welsh units">Welsh</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:5em">Asia</th><td class="navbox-list-with-group navbox-list navbox-even" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Afghan_units_of_measurement" title="Afghan units of measurement">Afghan</a></li> <li><a href="/wiki/Cambodian_units_of_measurement" title="Cambodian units of measurement">Cambodian</a></li> <li><a href="/wiki/Indian_units_of_measurement" title="Indian units of measurement">Indian</a></li> <li><a href="/wiki/Indonesian_units_of_measurement" title="Indonesian units of measurement">Indonesian</a></li> <li><a href="/wiki/Japanese_units_of_measurement" title="Japanese units of measurement">Japanese</a></li> <li><a href="/wiki/Korean_units_of_measurement" title="Korean units of measurement">Korean</a></li> <li><a href="/wiki/Mongolian_units" title="Mongolian units">Mongolian</a></li> <li><a href="/wiki/Myanmar_units_of_measurement" title="Myanmar units of measurement">Myanmar</a></li> <li><a href="/wiki/Nepalese_customary_units_of_measurement" title="Nepalese customary units of measurement">Nepalese</a></li> <li><a href="/wiki/Omani_units_of_measurement" title="Omani units of measurement">Omani</a></li> <li><a href="/wiki/History_of_measurement_systems_in_Pakistan" title="History of measurement systems in Pakistan">Pakistani</a></li> <li><a href="/wiki/Philippine_units_of_measurement" title="Philippine units of measurement">Philippine</a></li> <li><a href="/wiki/Abucco" title="Abucco">Pegu</a></li> <li><a href="/wiki/Singaporean_units_of_measurement" title="Singaporean units of measurement">Singaporean</a></li> <li><a href="/wiki/Sri_Lankan_units_of_measurement" title="Sri Lankan units of measurement">Sri Lankan</a></li> <li><a href="/wiki/Syrian_units_of_measurement" title="Syrian units of measurement">Syrian</a></li> <li><a href="/wiki/Taiwanese_units_of_measurement" title="Taiwanese units of measurement">Taiwanese</a></li> <li><a href="/wiki/Obsolete_Tatar_units_of_measurement" class="mw-redirect" title="Obsolete Tatar units of measurement">Tatar</a></li> <li><a href="/wiki/Thai_units_of_measurement" title="Thai units of measurement">Thai</a></li> <li><a href="/wiki/Vietnamese_units_of_measurement" title="Vietnamese units of measurement">Vietnamese</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:5em">Africa</th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Algerian_units_of_measurement" title="Algerian units of measurement">Algerian</a></li> <li><a href="/wiki/Ethiopian_units_of_measurement" title="Ethiopian units of measurement">Ethiopian</a></li> <li><a href="/wiki/Egyptian_units_of_measurement" title="Egyptian units of measurement">Egyptian</a></li> <li><a href="/wiki/Eritrean_units_of_measurement" title="Eritrean units of measurement">Eritrean</a></li> <li><a href="/wiki/Guinean_units_of_measurement" title="Guinean units of measurement">Guinean</a></li> <li><a href="/wiki/Libyan_units_of_measurement" title="Libyan units of measurement">Libyan</a></li> <li><a href="/wiki/Malagasy_units_of_measurement" title="Malagasy units of measurement">Malagasy</a></li> <li><a href="/wiki/Mauritian_units_of_measurement" title="Mauritian units of measurement">Mauritian</a></li> <li><a href="/wiki/Moroccan_units_of_measurement" title="Moroccan units of measurement">Moroccan</a></li> <li><a href="/wiki/Seychellois_units_of_measurement" title="Seychellois units of measurement">Seychellois</a></li> <li><a href="/wiki/Somali_units_of_measurement" title="Somali units of measurement">Somali</a></li> <li><a href="/wiki/South_African_units_of_measurement" title="South African units of measurement">South African</a></li> <li><a href="/wiki/Tunisian_units_of_measurement" title="Tunisian units of measurement">Tunisian</a></li> <li><a href="/wiki/Tanzanian_units_of_measurement" title="Tanzanian units of measurement">Tanzanian</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:5em">North America</th><td class="navbox-list-with-group navbox-list navbox-even" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Costa_Rican_units_of_measurement" title="Costa Rican units of measurement">Costa Rican</a></li> <li><a href="/wiki/Cuban_units_of_measurement" title="Cuban units of measurement">Cuban</a></li> <li><a href="/wiki/Haitian_units_of_measurement" title="Haitian units of measurement">Haitian</a></li> <li><a href="/wiki/Honduran_units_of_measurement" title="Honduran units of measurement">Honduran</a></li> <li><a href="/wiki/Mexican_units_of_measurement" title="Mexican units of measurement">Mexican</a></li> <li><a href="/wiki/Nicaraguan_units_of_measurement" title="Nicaraguan units of measurement">Nicaraguan</a></li> <li><a href="/wiki/Puerto_Rican_units_of_measurement" title="Puerto Rican units of measurement">Puerto Rican</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:5em">South America</th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Argentine_units_of_measurement" title="Argentine units of measurement">Argentine</a></li> <li><a href="/wiki/Bolivian_units_of_measurement" title="Bolivian units of measurement">Bolivian</a></li> <li><a href="/wiki/Brazilian_units_of_measurement" title="Brazilian units of measurement">Brazilian</a></li> <li><a href="/wiki/Chilean_units_of_measurement" title="Chilean units of measurement">Chilean</a></li> <li><a href="/wiki/Colombian_units_of_measurement" title="Colombian units of measurement">Colombian</a></li> <li><a href="/wiki/Paraguayan_units_of_measurement" title="Paraguayan units of measurement">Paraguayan</a></li> <li><a href="/wiki/Peruvian_units_of_measurement" title="Peruvian units of measurement">Peruvian</a></li> <li><a href="/wiki/Uruguayan_units_of_measurement" title="Uruguayan units of measurement">Uruguayan</a></li> <li><a href="/wiki/Venezuelan_units_of_measurement" title="Venezuelan units of measurement">Venezuelan</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Ancient</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Ancient_Arabic_units_of_measurement" title="Ancient Arabic units of measurement">Arabic</a></li> <li><a href="/wiki/Biblical_and_Talmudic_units_of_measurement" title="Biblical and Talmudic units of measurement">Biblical and Talmudic</a></li> <li><a href="/wiki/Ancient_Egyptian_units_of_measurement" title="Ancient Egyptian units of measurement">Egyptian</a></li> <li><a href="/wiki/Ancient_Greek_units_of_measurement" title="Ancient Greek units of measurement">Greek</a></li> <li><a href="/wiki/Hindu_units_of_time" title="Hindu units of time">Hindu</a></li> <li><a href="/wiki/History_of_measurement_systems_in_India" title="History of measurement systems in India">Indian</a></li> <li><a href="/wiki/Ancient_Mesopotamian_units_of_measurement" title="Ancient Mesopotamian units of measurement">Mesopotamian</a></li> <li><a href="/wiki/Persian_units_of_measurement" title="Persian units of measurement">Persian</a></li> <li><a href="/wiki/Ancient_Roman_units_of_measurement" title="Ancient Roman units of measurement">Roman</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">List articles</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/List_of_humorous_units_of_measurement" title="List of humorous units of measurement">Humorous</a></li> <li><a href="/wiki/List_of_obsolete_units_of_measurement" title="List of obsolete units of measurement">Obsolete</a></li> <li><a href="/wiki/List_of_unusual_units_of_measurement" title="List of unusual units of measurement">Unusual</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Other</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Absolute_scale" title="Absolute scale">Absolute scale</a></li> <li><a href="/wiki/N-body_units" title="N-body units">N-body</a></li> <li><a href="/wiki/Modulor" title="Modulor">Modulor</a></li></ul> </div></td></tr></tbody></table></div> <style data-mw-deduplicate="TemplateStyles:r1130092004">.mw-parser-output .portal-bar{font-size:88%;font-weight:bold;display:flex;justify-content:center;align-items:baseline}.mw-parser-output .portal-bar-bordered{padding:0 2em;background-color:#fdfdfd;border:1px solid #a2a9b1;clear:both;margin:1em auto 0}.mw-parser-output .portal-bar-related{font-size:100%;justify-content:flex-start}.mw-parser-output .portal-bar-unbordered{padding:0 1.7em;margin-left:0}.mw-parser-output .portal-bar-header{margin:0 1em 0 0.5em;flex:0 0 auto;min-height:24px}.mw-parser-output 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