Editing International System of Units (section)

== Organizational status ==

[[File:Metric and imperial systems (2019).svg|thumb|upright=1.3|Countries using the [[Metric system|metric]] (SI), [[Imperial units|imperial]], and [[US customary]] systems as of 2019]]
The International System of Units, or SI,<ref name="SIBrochure9thEd">{{Citation |last=International Bureau of Weights and Measures |title=The International System of Units (SI) |date=Dec 2022 |url=https://www.bipm.org/documents/20126/41483022/SI-Brochure-9-EN.pdf |volume=2 |issue=1 |archive-url=https://web.archive.org/web/20211018184555/https://www.bipm.org/documents/20126/41483022/SI-Brochure-9.pdf/fcf090b2-04e6-88cc-1149-c3e029ad8232 |url-status=live |edition=9th |isbn=978-92-822-2272-0 |archive-date=18 October 2021 |author-link=New SI}}</ref>{{rp|page=123|quote=... since its establishment in 1960, the International System of Units has always been referred to as "the SI" in its shortened form.}} is a [[decimal]] and [[metric system|metric]] [[system of units]] established in 1960 and periodically updated since then. The SI has an [[metrication|official status]] in most countries, including [[metrication in the United States|the United States]], [[metrication in Canada|Canada]], and [[metrication in the United Kingdom|the United Kingdom]], 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."<ref name="SIBrochure9thEd" />{{rp|pages=123,126}}

The only other types of measurement system that still have widespread use across the world are the [[imperial and US customary measurement systems]]. The [[international yard and pound]] are defined in terms of the SI.<ref name="Standards1959">{{cite book|author=United States. National Bureau of Standards|author-link=National Institute of Standards and Technology|title=Research Highlights of the National Bureau of Standards|url=https://books.google.com/books?id=4aWN-VRV1AoC&pg=PA13|access-date = 31 July 2019|year=1959|publisher=U.S. Department of Commerce, National Bureau of Standards|page=13}}</ref>

=== International System of Quantities ===

{{Main|International System of Quantities}}
The quantities and equations that provide the context in which the SI units are defined are now referred to as the ''[[International System of Quantities]]'' (ISQ).
The ISQ is based on the [[quantity#Quantity in physical science|quantities]] underlying each of the [[SI base units|seven base units of the SI]]. Other quantities, such as [[area]], [[pressure]], and [[electrical resistance]], are derived from these base quantities by clear, non-contradictory equations. The ISQ defines the quantities that are measured with the SI units.<ref>{{cite book |title=International vocabulary of metrology – Basic and general concepts and associated terms (VIM) |date=2012 |publisher=International Bureau of Weights and Measures (BIPM): Joint Committee for Guides in Metrology |edition=3rd |chapter-url=http://www.bipm.org/utils/common/documents/jcgm/JCGM_200_2012.pdf |access-date=28 March 2015 |chapter=1.16}}</ref> The ISQ is formalised, in part, in the international standard [[ISO/IEC 80000]], which was completed in 2009 with the publication of [[ISO 80000-1]],<ref>S. V. Gupta, ''Units of Measurement: Past, Present and Future. International System of Units'', p.&nbsp;16, Springer, 2009. {{ISBN|3642007384}}.</ref> and has largely been revised in 2019–2020.<ref>{{Cite web |title=ISO 80000-1:2022 Quantities and units Part 1: General |url=https://www.iso.org/standard/76921.html}}</ref>

=== Controlling authority ===

{{main | General Conference on Weights and Measures | International Bureau of Weights and Measures }}
The SI is regulated and continually developed by three international organisations that were established in 1875 under the terms of the [[Metre Convention]]. They are the [[General Conference on Weights and Measures]] (CGPM{{efn|name="French CGPM"|From [[French language|French]]: {{lang|fr|Conférence générale des poids et mesures.}}}}),<ref name="FR Interpretation of the SI">{{cite journal |date=16 May 2008 |title=Interpretation of the International System of Units (the Metric System of Measurement) for the United States |url=https://www.federalregister.gov/documents/2008/05/16/E8-11058/interpretation-of-the-international-system-of-units-the-metric-system-of-measurement-for-the-united |url-status=live |journal=[[Federal Register]] | publisher=[[National Institute of Standards and Technology]] | volume=73 |page=28432 |archive-url=https://web.archive.org/web/20170816003324/https://www.federalregister.gov/documents/2008/05/16/E8-11058/interpretation-of-the-international-system-of-units-the-metric-system-of-measurement-for-the-united |archive-date=16 August 2017 |access-date=6 December 2022}}</ref> the International Committee for Weights and Measures (CIPM{{efn|name="French CIPM"|from {{langx|fr|Comité international des poids et mesures}}}}), and the [[International Bureau of Weights and Measures]] (BIPM{{efn|name="BIPM from French"|from {{langx|fr|Bureau international des poids et mesures}}}}).
{{Anchor|SI Brochure}}All the decisions and recommendations concerning units are collected in a brochure called ''The International System of Units (SI)'',<ref name="SIBrochure9thEd" /> 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 [[international vocabulary of metrology]].<ref>{{cite web|url=http://www.bipm.org/en/publications/guides/vim.html|title= VIM3: International Vocabulary of Metrology |website=BIPM |url-status=dead |archive-url= https://web.archive.org/web/20201031042511/http://www.bipm.org/en/publications/guides/vim.html |archive-date= 31 October 2020 }}</ref> The brochure leaves some scope for local variations, particularly regarding unit names and terms in different languages. For example, the United States' [[National Institute of Standards and Technology]] (NIST) has produced a version of the CGPM document (NIST SP 330), which clarifies usage for English-language publications that use [[American English]].<ref name="NIST330">{{cite book |editor1=David B. Newell |editor2=Eite Tiesinga |title=The International System of Units (SI) |url=https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.330-2019.pdf |access-date=30 November 2019 |publisher=[[National Institute of Standards and Technology|NIST]] | location=Gaithersburg, MD |date=2019|edition=NIST Special publication 330, 2019}}</ref>