Editing International System of Units (section)

=== Unit symbols and the values of quantities ===

Symbols of SI units are intended to be unique and universal, independent of the context language.<ref name= "SIBrochure" />{{rp|pages=130–135}} The SI Brochure has specific rules for writing them.<ref name= "SIBrochure" />{{rp|pages=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.<ref name="SIBrochure9thEd"/>{{rp|page=147}}

In the United States, the guideline produced by the [[National Institute of Standards and Technology]] (NIST)<ref name= "NIST811">{{cite report |url=https://www.nist.gov/pml/special-publication-811 |title=Guide for the Use of the International System of Units (SI) |last1=Thompson |first1=Ambler |last2=Taylor |first2=Barry N. |date=March 2008 |publisher=[[National Institute of Standards and Technology]] | access-date=21 January 2022 |at=§10.5.3}}</ref>{{rp|page=37}} clarifies language-specific details for American English that were left unclear by the SI Brochure, but is otherwise identical to the SI Brochure.<ref name="NISTInterprepation">{{cite journal |date=9 May 2008 |url=http://edocket.access.gpo.gov/2008/pdf/E8-11058.pdf |title=Interpretation of the International System of Units (the Metric System of Measurement) for the United States |journal=Federal Register |volume=73 |issue=96 |pages=28432–28433 |id=FR Doc number E8-11058 |access-date=28 October 2009}}</ref> For example, since 1979, the [[litre]] may exceptionally be written using either an uppercase&nbsp;"L" or a lowercase&nbsp;"l", a decision prompted by the similarity of the lowercase letter&nbsp;"l" to the numeral&nbsp;"1", especially with certain typefaces or English-style handwriting. NIST recommends that within the United States, "L" be used rather than&nbsp;"l".<ref name="NIST811" />