Take the 2-minute tour ×
TeX - LaTeX Stack Exchange is a question and answer site for users of TeX, LaTeX, ConTeXt, and related typesetting systems. It's 100% free, no registration required.

Then I write


which yields an error:

! Undefined control sequence.
\vec #1->\mathbm 
l.564 \[\vec{a}
share|improve this question

1 Answer 1

up vote 6 down vote accepted

If you're interested in printing boldface mathematics, use \mathbf{...} instead:


Alternatively, you need to use

\usepackage{bm}% http://ctan.org/pkg/bm
\renewcommand{\vec}[1]{\bm{#1}}% Bold math

This shows the difference:

Difference between bm and mathbf

share|improve this answer
Thanks~ very useful –  dementrock Aug 22 '11 at 19:17

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.