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.
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
answered Apr 12 '11 at 20:27
TeX knows several modes, two of them are math mode and display math mode. Typesetting of ordinary text such as words nor numbers is different compared to mathematical formulas or a mathematical identifier such as x, which should look different from the text x (it does differ here in this editor only vaguely)
In order to let TeX know which mode should be used, there are indicators to enter math mode:
- Inline math mode, being entered
$and closed with$ - Display math mode, used with an enclosing
$$...$$in plainTeXor with\[...\]inLaTeX - Typing inside
\begin{math}...\end{math}inLaTeX - Several math environments in
LaTeXenter the math mode automatically, such asequation,align,alignedat,gatheretc.
Several characters/symbols being connected to math content require entering the math mode, such as \mathbb{R} etc.
I guess that an even better way to enter math mode is to use \( and \), as discussed in this answer.
\mathbbtypesets 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