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## Setting bold Greek letters in LaTeX

The issue here is complicated by the fact that \mathbf (the command for setting bold text in TeX maths) affects a select few mathematical symbols (the uppercase Greek letters). However lower-case Greek letters behave differently from upper-case Greek letters (due to Knuth’s esoteric font encoding decisions). However, \mathbf can’t be used even for upper-case Greek letters in the AMSLaTeX amsmath package, which disables this font-switching and you must use one of the techniques outlined below.

The Plain TeX solution does work, in a limited way:

{\boldmath$\theta$}


but \boldmath may not be used in maths mode, so this ‘solution’ requires arcana such as:

$... \mbox{\boldmath$\theta$} ...$


which then causes problems in superscripts, etc.

These problems may be addressed by using a bold mathematics package.

• The bm package, which is part of the LaTeX tools distribution, defines a command \bm which may be used anywhere in maths mode.
• The amsbsy package (which is part of AMSLaTeX) defines a command \boldsymbol, which (though slightly less comprehensive than \bm) covers almost all common cases.

All these solutions cover all mathematical symbols, not merely Greek letters.

bm.sty
Distributed as part of macros/latex/required/tools (or browse the directory); catalogue entry
amsbsy.sty
Distributed as part of AMSLaTeX macros/latex/required/amslatex (or browse the directory); catalogue entry
amsmath.sty
Distributed as part of AMSLaTeX macros/latex/required/amslatex (or browse the directory); catalogue entry

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URL for this question: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=boldgreek

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This is FAQ version 3.27, released on 2013-06-07.