# Bold Comma in Math Mode

$\mathbf{0,00042}$ A renders to

I think the comma could be a bit more bold. What do I wrong here?

Im using Arial as main font here:

  5 \setmainfont{Arial}
6
7 \usepackage[ngerman]{babel}
8
9 \usepackage{amsmath}
10 \usepackage{unicode-math}
11 \setmathfont{GFSNeohellenicMath.otf}
12 \setmathfont[range=up]{Arial}
13 \setmathfont[range=it]{Arial Italic}
14 \setmathfont[range=bfup]{Arial Bold}
15 \setmathfont[range=bfit]{Arial Bold Italic}
16 \setmathfont[range=tt]{Andale Mono}

• unlike \symbf, \mathbf selects the a different font rather than different unicode range so it depends which font you have set up for bold roman but it's hard to test as you have not provided a usable test file (and I don't have all the fonts used in your fragment) posting fragments (especially line numbered ) makes it harder for anyone to test answers. Apr 8 at 23:01
• Remark: You seem to be German or at least you use comma as a decimal separator. In that case, consider using 0{,}01 in order to remove the unwanted space after the comma. There are also packages for that, e. g. icomma. Update: I now see that this is already addressed in Davislor's answer :). Apr 9 at 2:16

You’re correct: \mathbf does not change the weight of symbols other than latters and numbers. The correct way to get a bold comma (or plus sign, etc.) is to set a bold math version.

As of 2021, there is no sans-serif math font that comes in a bold version, but you can fake one with fontspec commands. Unfortunately, the range= and version= options of \setmathfont do not work together. For this example, I picked Fira Sans and Fira Math.

\documentclass{article}
\usepackage{unicode-math}

\setmainfont{Fira Sans}
\setmathfont{Fira Math}
\setmathfont{Fira Math}[
version=bold,
FakeBold = 2.5]

\begin{document}
\noindent
$0{,}00042$ A \\
{\bfseries\boldmath
$0{,}00042$ A}
\end{document}


Tweak the value of FakeBold= to your taste. Writing the comma as {,} changes the math class to \mathord, which removes the spurious space you were getting after it. By default, TeX thinks that you have two numbers separated by a comma.

An alternative would be to use siunitx.