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href="https://bn.wikipedia.org/wiki/%E0%A6%AE%E0%A7%8C%E0%A6%B2%E0%A6%BF%E0%A6%95_%E0%A6%8F%E0%A6%95%E0%A6%95_(%E0%A6%AA%E0%A6%B0%E0%A6%BF%E0%A6%AE%E0%A6%BE%E0%A6%AA)" title="মৌলিক একক (পরিমাপ) – Bangla" lang="bn" hreflang="bn" data-title="মৌলিক একক (পরিমাপ)" data-language-autonym="বাংলা" data-language-local-name="Bangla" class="interlanguage-link-target"><span>বাংলা</span></a></li><li class="interlanguage-link interwiki-de badge-Q70894304 mw-list-item" title=""><a href="https://de.wikipedia.org/wiki/Basiseinheit" title="Basiseinheit – German" lang="de" hreflang="de" data-title="Basiseinheit" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Unidad_fundamental" title="Unidad fundamental – Spanish" lang="es" hreflang="es" data-title="Unidad fundamental" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/Unit%C3%A9_fondamentale" title="Unité fondamentale – French" lang="fr" hreflang="fr" data-title="Unité fondamentale" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-nn mw-list-item"><a href="https://nn.wikipedia.org/wiki/Grunneining" title="Grunneining – Norwegian Nynorsk" lang="nn" hreflang="nn" data-title="Grunneining" data-language-autonym="Norsk nynorsk" data-language-local-name="Norwegian Nynorsk" class="interlanguage-link-target"><span>Norsk nynorsk</span></a></li><li class="interlanguage-link interwiki-ro mw-list-item"><a href="https://ro.wikipedia.org/wiki/M%C4%83rimi_fizice_fundamentale" title="Mărimi fizice fundamentale – Romanian" lang="ro" hreflang="ro" data-title="Mărimi fizice fundamentale" data-language-autonym="Română" data-language-local-name="Romanian" class="interlanguage-link-target"><span>Română</span></a></li><li class="interlanguage-link interwiki-simple mw-list-item"><a href="https://simple.wikipedia.org/wiki/Base_unit_(measurement)" title="Base unit (measurement) – Simple English" lang="en-simple" hreflang="en-simple" data-title="Base unit (measurement)" data-language-autonym="Simple English" data-language-local-name="Simple English" class="interlanguage-link-target"><span>Simple English</span></a></li><li class="interlanguage-link interwiki-sv mw-list-item"><a href="https://sv.wikipedia.org/wiki/Grundenhet" title="Grundenhet – Swedish" lang="sv" hreflang="sv" data-title="Grundenhet" data-language-autonym="Svenska" data-language-local-name="Swedish" class="interlanguage-link-target"><span>Svenska</span></a></li><li class="interlanguage-link interwiki-th mw-list-item"><a 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class="vector-body" aria-labelledby="firstHeading" data-mw-ve-target-container> <div class="vector-body-before-content"> <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"><span class="mw-redirectedfrom">(Redirected from <a href="/w/index.php?title=Base_unit_(measurement)&redirect=no" class="mw-redirect" title="Base unit (measurement)">Base unit (measurement)</a>)</span></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">Unit of measurement adopted by convention for a base quantity</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">This article is about the type of unit of measure. For the concept in number theory, see <a href="/wiki/Fundamental_unit_(number_theory)" title="Fundamental unit (number theory)">Fundamental unit (number theory)</a>.</div> <style data-mw-deduplicate="TemplateStyles:r1251242444">.mw-parser-output .ambox{border:1px solid #a2a9b1;border-left:10px solid #36c;background-color:#fbfbfb;box-sizing:border-box}.mw-parser-output .ambox+link+.ambox,.mw-parser-output .ambox+link+style+.ambox,.mw-parser-output .ambox+link+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+style+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+link+.ambox{margin-top:-1px}html body.mediawiki .mw-parser-output .ambox.mbox-small-left{margin:4px 1em 4px 0;overflow:hidden;width:238px;border-collapse:collapse;font-size:88%;line-height:1.25em}.mw-parser-output .ambox-speedy{border-left:10px solid #b32424;background-color:#fee7e6}.mw-parser-output .ambox-delete{border-left:10px solid #b32424}.mw-parser-output .ambox-content{border-left:10px solid #f28500}.mw-parser-output .ambox-style{border-left:10px solid #fc3}.mw-parser-output .ambox-move{border-left:10px solid #9932cc}.mw-parser-output .ambox-protection{border-left:10px solid #a2a9b1}.mw-parser-output .ambox .mbox-text{border:none;padding:0.25em 0.5em;width:100%}.mw-parser-output .ambox .mbox-image{border:none;padding:2px 0 2px 0.5em;text-align:center}.mw-parser-output .ambox .mbox-imageright{border:none;padding:2px 0.5em 2px 0;text-align:center}.mw-parser-output .ambox .mbox-empty-cell{border:none;padding:0;width:1px}.mw-parser-output .ambox .mbox-image-div{width:52px}@media(min-width:720px){.mw-parser-output .ambox{margin:0 10%}}@media print{body.ns-0 .mw-parser-output .ambox{display:none!important}}</style><table class="box-More_citations_needed plainlinks metadata ambox ambox-content ambox-Refimprove" role="presentation"><tbody><tr><td class="mbox-image"><div class="mbox-image-div"><span typeof="mw:File"><a href="/wiki/File:Question_book-new.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/50px-Question_book-new.svg.png" decoding="async" width="50" height="39" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/75px-Question_book-new.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/100px-Question_book-new.svg.png 2x" data-file-width="512" data-file-height="399" /></a></span></div></td><td class="mbox-text"><div class="mbox-text-span">This article <b>needs additional citations for <a href="/wiki/Wikipedia:Verifiability" title="Wikipedia:Verifiability">verification</a></b>.<span class="hide-when-compact"> Please help <a href="/wiki/Special:EditPage/Base_unit_of_measurement" title="Special:EditPage/Base unit of measurement">improve this article</a> by <a href="/wiki/Help:Referencing_for_beginners" title="Help:Referencing for beginners">adding citations to reliable sources</a>. Unsourced material may be challenged and removed.<br /><small><span class="plainlinks"><i>Find sources:</i> <a rel="nofollow" class="external text" href="https://www.google.com/search?as_eq=wikipedia&q=%22Base+unit+of+measurement%22">"Base unit of measurement"</a> – <a rel="nofollow" class="external text" href="https://www.google.com/search?tbm=nws&q=%22Base+unit+of+measurement%22+-wikipedia&tbs=ar:1">news</a> <b>·</b> <a rel="nofollow" class="external text" href="https://www.google.com/search?&q=%22Base+unit+of+measurement%22&tbs=bkt:s&tbm=bks">newspapers</a> <b>·</b> <a rel="nofollow" class="external text" href="https://www.google.com/search?tbs=bks:1&q=%22Base+unit+of+measurement%22+-wikipedia">books</a> <b>·</b> <a rel="nofollow" class="external text" href="https://scholar.google.com/scholar?q=%22Base+unit+of+measurement%22">scholar</a> <b>·</b> <a rel="nofollow" class="external text" href="https://www.jstor.org/action/doBasicSearch?Query=%22Base+unit+of+measurement%22&acc=on&wc=on">JSTOR</a></span></small></span> <span class="date-container"><i>(<span class="date">March 2013</span>)</i></span><span class="hide-when-compact"><i> (<small><a href="/wiki/Help:Maintenance_template_removal" title="Help:Maintenance template removal">Learn how and when to remove this message</a></small>)</i></span></div></td></tr></tbody></table> <p>A <b>base unit of measurement</b> (also referred to as a <b>base unit</b> or <b>fundamental unit</b>) is a <a href="/wiki/Unit_of_measurement" title="Unit of measurement">unit of measurement</a> adopted for a <i><a href="/wiki/Base_quantity" class="mw-redirect" title="Base quantity">base quantity</a></i>. A base quantity is one of a conventionally chosen subset of <a href="/wiki/Physical_quantity" title="Physical quantity">physical quantities</a>, where no quantity in the subset can be expressed in terms of the others. The <a href="/wiki/SI_base_units" class="mw-redirect" title="SI base units">SI base units</a>, or <i>Systéme International d'unités</i>, consists of the metre, kilogram, second, ampere, kelvin, mole and candela. </p><p>A <b>unit multiple</b> (or <b>multiple of a unit</b>) is an integer <a href="/wiki/Multiple_(mathematics)" title="Multiple (mathematics)">multiple</a> of a given unit; likewise a <b>unit submultiple</b> (or <b>submultiple of a unit</b>) is a <a href="/wiki/Submultiple" class="mw-redirect" title="Submultiple">submultiple</a> or a <a href="/wiki/Unit_fraction" title="Unit fraction">unit fraction</a> of a given unit.<sup id="cite_ref-80000-1:2009_1-0" class="reference"><a href="#cite_note-80000-1:2009-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> <i><a href="/wiki/Unit_prefix" title="Unit prefix">Unit prefixes</a></i> are common base-10 or base-2 powers multiples and submultiples of units. </p><p>While a base unit is one that has been explicitly so designated,<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> a <b>derived unit</b> is unit for a <i><a href="/wiki/Derived_quantity" class="mw-redirect" title="Derived quantity">derived quantity</a></i>, involving the combination of quantities with different units;<sup id="cite_ref-80000-1:2009_1-1" class="reference"><a href="#cite_note-80000-1:2009-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> several <i><a href="/wiki/SI_derived_units" class="mw-redirect" title="SI derived units">SI derived units</a></i> are specially named. A <i><a href="/wiki/Coherent_derived_unit" class="mw-redirect" title="Coherent derived unit">coherent derived unit</a></i> involves no <a href="/wiki/Conversion_factor" class="mw-redirect" title="Conversion factor">conversion factors</a>. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Background">Background</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Base_unit_of_measurement&action=edit&section=1" title="Edit section: Background"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In the language of <a href="/wiki/Measurement" title="Measurement">measurement</a>, <i><a href="/wiki/Physical_quantities" class="mw-redirect" title="Physical quantities">physical quantities</a></i> are <a href="/wiki/Quantifiable" class="mw-redirect" title="Quantifiable">quantifiable</a> aspects of the world, such as <a href="/wiki/Time" title="Time">time</a>, <a href="/wiki/Distance" title="Distance">distance</a>, <a href="/wiki/Velocity" title="Velocity">velocity</a>, <a href="/wiki/Mass" title="Mass">mass</a>, <a href="/wiki/Temperature" title="Temperature">temperature</a>, <a href="/wiki/Energy" title="Energy">energy</a>, and <a href="/wiki/Weight" title="Weight">weight</a>, and <i>units</i> are used to describe their magnitude or quantity. Many of these quantities are related to each other by various physical laws, and as a result the units of a quantities can be generally be expressed as a product of powers of other units; for example, momentum is mass multiplied by velocity, while velocity is distance divided by time. These relationships are discussed in <a href="/wiki/Dimensional_analysis" title="Dimensional analysis">dimensional analysis</a>. Those that can be expressed in this fashion in terms of the base units are called <a href="/wiki/Derived_unit_(measurement)" class="mw-redirect" title="Derived unit (measurement)">derived units</a>. </p> <div class="mw-heading mw-heading2"><h2 id="International_System_of_Units">International System of Units</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Base_unit_of_measurement&action=edit&section=2" title="Edit section: International System of Units"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></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/SI_base_units" class="mw-redirect" title="SI base units">SI base units</a> and <a href="/wiki/SI_derived_units" class="mw-redirect" title="SI derived units">SI derived units</a></div> <p>In the <a href="/wiki/International_System_of_Units" title="International System of Units">International System of Units</a> (SI), there are seven base units: <a href="/wiki/Kilogram" title="Kilogram">kilogram</a>, <a href="/wiki/Metre" title="Metre">metre</a>, <a href="/wiki/Candela" title="Candela">candela</a>, <a href="/wiki/Second" title="Second">second</a>, <a href="/wiki/Ampere" title="Ampere">ampere</a>, <a href="/wiki/Kelvin" title="Kelvin">kelvin</a>, and <a href="/wiki/Mole_(unit)" title="Mole (unit)">mole</a>. Several derived units have been defined, many with special names and symbols. </p><p>In 2019 the seven SI base units were redefined in terms of seven defining constants. Therefore the SI base units are no longer necessary but were retained because for historical and practical reasons.<sup id="cite_ref-Brochure9_2019_3-0" class="reference"><a href="#cite_note-Brochure9_2019-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> See <i><a href="/wiki/2019_revision_of_the_SI" title="2019 revision of the SI">2019 revision of the SI</a></i>. </p> <div class="mw-heading mw-heading2"><h2 id="Natural_units">Natural units</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Base_unit_of_measurement&action=edit&section=3" title="Edit section: Natural units"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></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/Natural_units" title="Natural units">Natural units</a></div> <p>A set of base dimensions of quantity is a minimal set of units such that every physical quantity can be expressed in terms of this set. The traditional base dimensions are <a href="/wiki/Mass" title="Mass">mass</a>, <a href="/wiki/Length" title="Length">length</a>, <a href="/wiki/Time" title="Time">time</a>, <a href="/wiki/Electric_charge" title="Electric charge">charge</a>, and <a href="/wiki/Temperature" title="Temperature">temperature</a>, but in principle, other base quantities could be used. <a href="/wiki/Electric_current" title="Electric current">Electric current</a> could be used instead of charge or <a href="/wiki/Speed" title="Speed">speed</a> could be used instead of length. Some physicists have not recognized temperature as a base dimension since it simply expresses the energy per particle per degree of freedom which can be expressed in terms of energy (or mass, length, and time).<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> Duff argues that only dimensionless values have physical meaning and all dimensional units are human constructs.<sup id="cite_ref-hep-th1412.2040_5-0" class="reference"><a href="#cite_note-hep-th1412.2040-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> </p><p>There are other relationships between physical quantities that can be expressed by means of fundamental constants, and to some extent it is an arbitrary decision whether to retain the fundamental constant as a quantity with dimensions or simply to define it as unity or a fixed <a href="/wiki/Dimensionless_quantity" title="Dimensionless quantity">dimensionless number</a>, and reduce the number of explicit base quantities by one. The <a href="/wiki/Ontological" class="mw-redirect" title="Ontological">ontological</a> issue is whether these fundamental constants really exist as dimensional or dimensionless quantities. This is equivalent to treating length as the same as time or understanding electric charge as a combination of quantities of mass, length, and time which may seem less natural than thinking of temperature as measuring the same material as energy (which is expressible in terms of mass, length, and time). </p><p>For instance, time and distance are related to each other by the <a href="/wiki/Speed_of_light" title="Speed of light">speed of light</a>, <i>c</i>, which is a fundamental constant. It is possible to use this relationship to eliminate either the base unit of time or that of distance. Similar considerations apply to the <a href="/wiki/Planck_constant" title="Planck constant">Planck constant</a>, <i>h</i>, which relates energy (with dimension expressible in terms of mass, length and time) to frequency (with dimension expressible in terms of time). In theoretical physics it is customary to use such units (natural units) in which <span class="nowrap"><i>c</i> = 1</span> and <span class="nowrap"><i>ħ</i> = 1</span>. A similar choice can be applied to the <a href="/wiki/Vacuum_permittivity" title="Vacuum permittivity">vacuum permittivity</a>, <i>ε</i><sub>0</sub>. </p> <ul><li>One could eliminate either the metre or the second by setting <i>c</i> to unity (or to any other fixed dimensionless number).</li> <li>One could then eliminate the kilogram by setting <i>ħ</i> to a dimensionless number.</li> <li>One could eliminate the ampere by setting either the vacuum permittivity <i>ε</i><sub>0</sub> or the <a href="/wiki/Elementary_charge" title="Elementary charge">elementary charge</a> <i>e</i> to a dimensionless number.</li> <li>One could eliminate the mole as a base unit by setting the <a href="/wiki/Avogadro_constant" title="Avogadro constant">Avogadro constant</a> <i>N</i><sub>A</sub> to 1. This is natural as it is a technical scaling constant.</li> <li>One could eliminate the kelvin as it can be argued that temperature simply expresses the energy per particle per <a href="/wiki/Degree_of_freedom" class="mw-redirect" title="Degree of freedom">degree of freedom</a>, which can be expressed in terms of energy (or mass, length, and time). Another way of saying this is that the <a href="/wiki/Boltzmann_constant" title="Boltzmann constant">Boltzmann constant</a> <i>k</i><sub>B</sub> is a technical scaling constant and could be set to a fixed dimensionless number.</li> <li>Similarly, one could eliminate the candela, as that is defined in terms of other physical quantities via a technical scaling constant, <i>K</i><sub>cd</sub>.</li> <li>That leaves one base dimension and an associated base unit, but there are several fundamental constants left to eliminate that too – for instance, one could use <i>G</i>, the <a href="/wiki/Gravitational_constant" title="Gravitational constant">gravitational constant</a>, <i>m</i><sub>e</sub>, the <a href="/wiki/Electron_rest_mass" class="mw-redirect" title="Electron rest mass">electron rest mass</a>, or Λ, the <a href="/wiki/Cosmological_constant" title="Cosmological constant">cosmological constant</a>.</li></ul> <p>The preferred choices vary by the field in physics. Using natural units leaves every physical quantity expressed as a dimensionless number, which is noted by physicists disputing the existence of incompatible base quantities.<sup id="cite_ref-hep-th1412.2040_5-1" class="reference"><a href="#cite_note-hep-th1412.2040-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Base_unit_of_measurement&action=edit&section=4" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Characteristic_units" class="mw-redirect" title="Characteristic units">Characteristic units</a></li> <li><a href="/wiki/Dimensional_analysis" title="Dimensional analysis">Dimensional analysis</a></li> <li><a href="/wiki/Natural_units" title="Natural units">Natural units</a></li> <li><a href="/wiki/One_(unit)" class="mw-redirect" title="One (unit)">One (unit)</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Base_unit_of_measurement&action=edit&section=5" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <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-80000-1:2009-1"><span class="mw-cite-backlink">^ <a href="#cite_ref-80000-1:2009_1-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-80000-1:2009_1-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><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 a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.iso.org/standard/30669.html">"ISO 80000-1:2009"</a>. <a href="/wiki/International_Organization_for_Standardization" title="International Organization for Standardization">International Organization for Standardization</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20190702201943/https://www.iso.org/standard/30669.html">Archived</a> from the original on 2019-07-02<span class="reference-accessdate">. Retrieved <span class="nowrap">2019-09-15</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=ISO+80000-1%3A2009&rft.pub=International+Organization+for+Standardization&rft_id=https%3A%2F%2Fwww.iso.org%2Fstandard%2F30669.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ABase+unit+of+measurement" class="Z3988"></span></span> </li> <li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text"> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFTaylorThompson2008" class="citation book cs1">Taylor, Barry N.; Thompson, Ambler (2008). <a rel="nofollow" class="external text" href="https://archive.org/details/internationalsys3309tayl"><i>The International System of Units (SI)</i></a>. Washington, D.C.: U.S. Department of Commerce. p. 56 (10th CGPM, 1954, Resolution 6).</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+International+System+of+Units+%28SI%29&rft.place=Washington%2C+D.C.&rft.pages=p.+56+%2810th+CGPM%2C+1954%2C+Resolution+6%29&rft.pub=U.S.+Department+of+Commerce&rft.date=2008&rft.aulast=Taylor&rft.aufirst=Barry+N.&rft.au=Thompson%2C+Ambler&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Finternationalsys3309tayl&rfr_id=info%3Asid%2Fen.wikipedia.org%3ABase+unit+of+measurement" class="Z3988"></span></span> </li> <li id="cite_note-Brochure9_2019-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-Brochure9_2019_3-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.bipm.org/en/publications/si-brochure/">"9th edition of the SI Brochure"</a>. BIPM. 2019. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20210419211921/https://www.bipm.org/en/publications/si-brochure">Archived</a> from the original on 19 April 2021<span class="reference-accessdate">. Retrieved <span class="nowrap">20 May</span> 2019</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=9th+edition+of+the+SI+Brochure&rft.pub=BIPM&rft.date=2019&rft_id=https%3A%2F%2Fwww.bipm.org%2Fen%2Fpublications%2Fsi-brochure%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3ABase+unit+of+measurement" class="Z3988"></span></span> </li> <li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFQuinceyBrown2017" class="citation journal cs1">Quincey, Paul; Brown, Richard J C (2017-08-01). <a rel="nofollow" class="external text" href="https://iopscience.iop.org/article/10.1088/1681-7575/aa7160">"A clearer approach for defining unit systems"</a>. <i>Metrologia</i>. <b>54</b> (4): 454–460. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/1705.03765">1705.03765</a></span>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1088%2F1681-7575%2Faa7160">10.1088/1681-7575/aa7160</a>. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/0026-1394">0026-1394</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Metrologia&rft.atitle=A+clearer+approach+for+defining+unit+systems&rft.volume=54&rft.issue=4&rft.pages=454-460&rft.date=2017-08-01&rft_id=info%3Aarxiv%2F1705.03765&rft.issn=0026-1394&rft_id=info%3Adoi%2F10.1088%2F1681-7575%2Faa7160&rft.aulast=Quincey&rft.aufirst=Paul&rft.au=Brown%2C+Richard+J+C&rft_id=https%3A%2F%2Fiopscience.iop.org%2Farticle%2F10.1088%2F1681-7575%2Faa7160&rfr_id=info%3Asid%2Fen.wikipedia.org%3ABase+unit+of+measurement" class="Z3988"></span></span> </li> <li id="cite_note-hep-th1412.2040-5"><span class="mw-cite-backlink">^ <a href="#cite_ref-hep-th1412.2040_5-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-hep-th1412.2040_5-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFMichael_Duff2015" class="citation journal cs1"><a href="/wiki/Michael_Duff_(physicist)" title="Michael Duff (physicist)">Michael Duff</a> (2015). <span class="id-lock-subscription" title="Paid subscription required"><a rel="nofollow" class="external text" href="https://www.tandfonline.com/doi/abs/10.1080/00107514.2014.980093">"How fundamental are fundamental constants?"</a></span>. <i>Contemporary Physics</i>. <b>56</b> (1): 35–47. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/1412.2040">1412.2040</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2015ConPh..56...35D">2015ConPh..56...35D</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1080%2F00107514.2014.980093">10.1080/00107514.2014.980093</a>. <a href="/wiki/Hdl_(identifier)" class="mw-redirect" title="Hdl (identifier)">hdl</a>:<a rel="nofollow" class="external text" href="https://hdl.handle.net/10044%2F1%2F68485">10044/1/68485</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:118347723">118347723</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20211122065250/https://www.tandfonline.com/doi/abs/10.1080/00107514.2014.980093">Archived</a> from the original on 2021-11-22<span class="reference-accessdate">. Retrieved <span class="nowrap">2020-04-03</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Contemporary+Physics&rft.atitle=How+fundamental+are+fundamental+constants%3F&rft.volume=56&rft.issue=1&rft.pages=35-47&rft.date=2015&rft_id=info%3Ahdl%2F10044%2F1%2F68485&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A118347723%23id-name%3DS2CID&rft_id=info%3Abibcode%2F2015ConPh..56...35D&rft_id=info%3Aarxiv%2F1412.2040&rft_id=info%3Adoi%2F10.1080%2F00107514.2014.980093&rft.au=Michael+Duff&rft_id=https%3A%2F%2Fwww.tandfonline.com%2Fdoi%2Fabs%2F10.1080%2F00107514.2014.980093&rfr_id=info%3Asid%2Fen.wikipedia.org%3ABase+unit+of+measurement" class="Z3988"></span></span> </li> <li id="cite_note-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-6">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFJackson1998" class="citation book cs1">Jackson, John David (1998). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20140113162927/http://homepages.spa.umn.edu/~kd/Ast8001/em_units.pdf">"Appendix on Units and Dimensions"</a> <span class="cs1-format">(PDF)</span>. <i>Classical Electrodynamics</i>. John Wiley and Sons. p. 775. Archived from <a rel="nofollow" class="external text" href="http://homepages.spa.umn.edu/~kd/Ast8001/em_units.pdf">the original</a> <span class="cs1-format">(PDF)</span> on 13 January 2014<span class="reference-accessdate">. Retrieved <span class="nowrap">13 January</span> 2014</span>. <q>The <i>arbitrariness</i> in the number of fundamental units and in the dimensions of any physical quantity in terms of those units has been emphasized by Abraham, Plank, Bridgman, Birge, and others.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Appendix+on+Units+and+Dimensions&rft.btitle=Classical+Electrodynamics&rft.pages=775&rft.pub=John+Wiley+and+Sons&rft.date=1998&rft.aulast=Jackson&rft.aufirst=John+David&rft_id=http%3A%2F%2Fhomepages.spa.umn.edu%2F~kd%2FAst8001%2Fem_units.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3ABase+unit+of+measurement" class="Z3988"></span></span> </li> <li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBirge1935" class="citation journal cs1">Birge, Raymond T. (1935). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20150923221228/http://www.brynmawr.edu/physics/DJCross/docs/files/birge2.pdf">"On the establishment of fundamental and derived units, with special reference to electric units. Part I."</a> <span class="cs1-format">(PDF)</span>. <i>American Journal of Physics</i>. <b>3</b> (3): 102–109. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1935AmJPh...3..102B">1935AmJPh...3..102B</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1119%2F1.1992945">10.1119/1.1992945</a>. Archived from <a rel="nofollow" class="external text" href="http://www.brynmawr.edu/physics/DJCross/docs/files/birge2.pdf">the original</a> <span class="cs1-format">(PDF)</span> on 23 September 2015<span class="reference-accessdate">. Retrieved <span class="nowrap">13 January</span> 2014</span>. <q>Because, however, of the arbitrary character of dimensions, as presented so ably by Bridgman, the choice and number of fundamental units are arbitrary.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=American+Journal+of+Physics&rft.atitle=On+the+establishment+of+fundamental+and+derived+units%2C+with+special+reference+to+electric+units.+Part+I.&rft.volume=3&rft.issue=3&rft.pages=102-109&rft.date=1935&rft_id=info%3Adoi%2F10.1119%2F1.1992945&rft_id=info%3Abibcode%2F1935AmJPh...3..102B&rft.aulast=Birge&rft.aufirst=Raymond+T.&rft_id=http%3A%2F%2Fwww.brynmawr.edu%2Fphysics%2FDJCross%2Fdocs%2Ffiles%2Fbirge2.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3ABase+unit+of+measurement" class="Z3988"></span></span> </li> </ol></div></div>    </div><noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?type=1x1" alt="" width="1" height="1" style="border: none; position: absolute;"></noscript> <div class="printfooter" data-nosnippet="">Retrieved from "<a dir="ltr" href="https://en.wikipedia.org/w/index.php?title=Base_unit_of_measurement&oldid=1244912506">https://en.wikipedia.org/w/index.php?title=Base_unit_of_measurement&oldid=1244912506</a>"</div></div> <div id="catlinks" class="catlinks" data-mw="interface"><div id="mw-normal-catlinks" class="mw-normal-catlinks"><a href="/wiki/Help:Category" title="Help:Category">Categories</a>: <ul><li><a href="/wiki/Category:Measurement" title="Category:Measurement">Measurement</a></li><li><a href="/wiki/Category:Dimensional_analysis" title="Category:Dimensional analysis">Dimensional analysis</a></li></ul></div><div id="mw-hidden-catlinks" class="mw-hidden-catlinks mw-hidden-cats-hidden">Hidden categories: <ul><li><a href="/wiki/Category:Articles_with_short_description" title="Category:Articles with short description">Articles with short description</a></li><li><a href="/wiki/Category:Short_description_matches_Wikidata" title="Category:Short description matches Wikidata">Short description matches Wikidata</a></li><li><a href="/wiki/Category:Articles_needing_additional_references_from_March_2013" title="Category:Articles needing additional references from March 2013">Articles needing additional references from March 2013</a></li><li><a href="/wiki/Category:All_articles_needing_additional_references" title="Category:All articles needing additional references">All articles needing additional references</a></li></ul></div></div> </div> </main> </div> <div class="mw-footer-container"> <footer id="footer" class="mw-footer" > <ul id="footer-info"> <li id="footer-info-lastmod"> This page was last edited on 9 September 2024, at 22:27<span class="anonymous-show"> (UTC)</span>.</li> <li id="footer-info-copyright">Text is available under the <a href="/wiki/Wikipedia:Text_of_the_Creative_Commons_Attribution-ShareAlike_4.0_International_License" title="Wikipedia:Text of the Creative Commons Attribution-ShareAlike 4.0 International License">Creative Commons Attribution-ShareAlike 4.0 License</a>; additional terms may apply. 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