# Comma not working inside \bm when using babel

When I try to compile this simple document

\documentclass{article}
\usepackage[italian]{babel}
\usepackage{bm}

\begin{document}
$\bm{,}$
\end{document}


! Undefined control sequence.
\it@comma@def  ->\futurelet \let@token
\@@math@comma
l.7 $\bm{,}$


and a strange number (25915) is printed on the resulting pdf instead of the comma.
Something odd is going on with the babel package, because if I remove the line

\usepackage[italian]{babel}


everything works just fine.

Any thoughts?

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Welcome to TeX.SX! –  egreg May 12 '14 at 9:17

Unfortunately, the “intelligent comma” commands proposed in italian.ldf are not really smart.

You can avoid the problem with \bm by using

\bm{\mathpunct{,}}


or

\bm{{,}}


depending if you want it to be punctuation or an ordinary symbol.

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Great answer, thank you! –  Mizar May 12 '14 at 9:26