TeX - LaTeX Stack Exchange is a question and answer site for users of TeX, LaTeX, ConTeXt, and related typesetting systems. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I'm new to Tex and tried to enter an equation using \mathbb. I received a prompt

LaTeX Error: \mathbb allowed only in math mode.
See the LaTeX manual or LaTeX Companion for explanation.

I thought I would try here for an explanation

share|improve this question
Phil's answer below is correct, but a further tip: the macro \mathbb typesets capital letters as "black-board bold" symbols, such as the symbol ℝ which usually denotes the set of real numbers (and which is produced by \mathbb{R} in math mode). – Niel de Beaudrap Apr 14 '11 at 6:48
up vote 7 down vote accepted

You enter math mode by typing a dollar sign $, and you leave math mode by typing another dollar sign $. You should take a look at Chapter 3 of The Not So Short Introduction to LaTeX

share|improve this answer

I guess that an even better way to enter math mode is to use \( and \), as discussed in this answer.

share|improve this answer

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.