# siunitx and \meter

I've found (here in french https://fr.wikibooks.org/wiki/LaTeX/%C3%89crire_de_la_physique#Extension_siunitx) that I could use the package siunitx to write the unit but it doesn't work :

A minimal code to test :

\documentclass[a4paper]{article}

\usepackage{siunitx}

\title{Test}
\author{Cécile Moulin}
\date{}

\begin{document}
\maketitle
\tableofcontents

text text text
\metre

\end{document}


The error :

This is pdfTeX, Version 3.14159265-2.6-1.40.16 (TeX Live 2015/Debian) (preloaded format=pdflatex)
restricted \write18 enabled.
entering extended mode
(./test.tex
LaTeX2e <2016/02/01>
Babel <3.9q> and hyphenation patterns for 81 language(s) loaded.
(/usr/share/texlive/texmf-dist/tex/latex/base/article.cls
Document Class: article 2014/09/29 v1.4h Standard LaTeX document class
(/usr/share/texlive/texmf-dist/tex/latex/base/size10.clo))
(/usr/share/texlive/texmf-dist/tex/latex/siunitx/siunitx.sty
(/usr/share/texlive/texmf-dist/tex/latex/l3kernel/expl3.sty
(/usr/share/texlive/texmf-dist/tex/latex/l3kernel/expl3-code.tex)
(/usr/share/texlive/texmf-dist/tex/latex/l3kernel/l3pdfmode.def))
(/usr/share/texlive/texmf-dist/tex/latex/l3packages/xparse/xparse.sty)
(/usr/share/texlive/texmf-dist/tex/latex/amsmath/amstext.sty
(/usr/share/texlive/texmf-dist/tex/latex/amsmath/amsgen.sty))
(/usr/share/texlive/texmf-dist/tex/latex/tools/array.sty)
(/usr/share/texlive/texmf-dist/tex/latex/l3packages/l3keys2e/l3keys2e.sty)
(/usr/share/texlive/texmf-dist/tex/latex/beamer/translator/translator.sty
(/usr/share/texlive/texmf-dist/tex/latex/graphics/keyval.sty)
(/usr/share/texlive/texmf-dist/tex/latex/beamer/translator/translator-language-
mappings.tex))) (./test.aux)
(/usr/share/texlive/texmf-dist/tex/latex/beamer/translator/dicts/translator-bas
ic-dictionary/translator-basic-dictionary-English.dict)
(/usr/share/texlive/texmf-dist/tex/latex/siunitx/siunitx-abbreviations.cfg)
(./test.toc)
! Undefined control sequence.
\metre ->\ERROR

l.18 \metre


I've tried with/without  and with \meter too, it's the same

• In order not to disturb the rest of the document the unit macros can only be used in the second argument to \SI{}{} or in the argument to \si{}. The first is used to typeset value+unit and the later is used to typeset just a unit. So use \si{\metre} instead of \metre. – daleif Jun 12 '17 at 14:02

Normally these units only work within \si{...} (and similar commands), but if you want to use them in normal text, you can use the free-standing-units=true of the siunitx package.

\documentclass{article}

\usepackage[free-standing-units=true]{siunitx}

\begin{document}

\si{\metre} % for the unit alone

\SI{42}{\metre} % for value and unit

\metre % this needs free-standing-units=true

\SI{10}{\nano\meter}

\SI{10}{\nm}

\SI{10}{nm}

\end{document}

• Where can I find documentation about \SI{}{} ? I didn't find... So, the first part is for the value. What about nano and cie ? I have a unit which is '10 nm', so I think that the 10 is in the second part but is it true ? – Ccile Jun 12 '17 at 14:09
• @Ccile You can find the documentation of siunitx at texdoc.net/texmf-dist/doc/latex/siunitx/siunitx.pdf -- for the 10 nm, please see my updated answer, \nano is prefix to meter. Why would 10 be the second part? – samcarter_is_at_topanswers.xyz Jun 12 '17 at 14:12
• Ok, thanks. For 10 nm, you think it's better so or I can't do another way ? – Ccile Jun 12 '17 at 14:17
• @Ccile Sorry, I don't understand your last comment, can you rephrase the question? – samcarter_is_at_topanswers.xyz Jun 12 '17 at 14:19
• @Ccile The unit and the number should be separate \SI{10}{\nm} or \SI{10}{\nano\metre}. For exponents, do you mean \SI{10e-21}{\metre} perhaps? – Joseph Wright Jun 12 '17 at 14:26