# Special Symbol “::=”

As the title says, does LaTeX have this special symbol:

::=


I tried to look at some cheat-sheets and http://detexify.kirelabs.org/classify.html but could not find it.

• There is also a \vcentcolon in the mathtools package that has a := symbol with only one colon. Here is a question related to the question of modifying the look of these symbols: tex.stackexchange.com/questions/125023/… – Steven B. Segletes Mar 24 '15 at 10:50

Yes, it is called \Coloneqq and it's defined by the mathtools package, which is an extension of amsmath.

MWE

\documentclass{article}
\usepackage{mathtools}

\begin{document}
$\Coloneqq$
\end{document}


The package also provides other symbols like the above one (see subsubsection 3.7.3 of the documentation) including \vcentcolon which is a colon properly vertically centered.

Moreover, issuing

\mathtoolsset{centercolon}


you can have all your math colons (including the \colon command) properly vertically centered.

Example:

\documentclass{article}
\usepackage{mathtools}
\mathtoolsset{centercolon}

\begin{document}
$\colon \quad : \quad \coloneqq \quad \Coloneqq$
\end{document}


Package colonequals provides such symbols with properly vertically centered colons:

\documentclass{article}
\usepackage{colonequals}

\begin{document}
$A \coloncolonequals B$
\end{document}


# OpenType fonts

If the TeX engine supports OpenType fonts (LuaTeX, XeTeX), then the symbol can be used directly as Unicode symbol ⩴ (U+2A74) or macro \Coloneq, if package unicode-math with a font, which contains this symbol.

When testing fonts, \tracinglostchars=2 is useful, because then missing characters are also logged on the screen, e.g.:

Missing character: There is no ⩴ (U+2A74) in font "[latinmodern-math]:mode=base;script=math;language=DFLT;"!


## Asana-Math

\documentclass{article}
\usepackage{unicode-math}
\setmathfont{Asana-Math.otf}
\begin{document}
$A \Coloneq B$
\end{document}


## XITS Math

\setmathfont{xits-math.otf}

If you needn't to use any packages, you can define the symbol:

\def\cceq{\mathrel{\vcenter{\hbox{::}}{=}}}

$$A \cceq B$$
\bye