In mathematical mode as well as in text mode, you can change the typeface as needed. For instance, it's customary to represent real numbers with a blackboard bold font, or topological spaces with calligraphic font. This article shows several fonts for use in math mode.

[edit] Introduction

For some elements is convenient to have the possibility of changing the font typeface.

Let \( \mathcal{T} \) be a topological space, a basis is defined as
 \[
 \mathcal{B} = \{B_{\alpha} \in \mathcal{T}\, |\,  U = \bigcup B_{\alpha} \forall U \in \mathcal{T} \}
  \]

Several fonts require the addition of the line \usepackage{amssymb} to the preamble to work.

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[edit] Capital letters-only font typefaces

There are some font typefaces that support only a limited number of characters; these fonts usually denote some special sets.

\begin{align*}
RQSZ \\
\mathcal{RQSZ} \\
\mathfrak{RQSZ} \\
\mathbb{RQSZ}
\end{align*}

This example shows Calligraphic, Fraktur and Blackboard bold typefaces. For instance, to display the R in blackboard bold typeface $\mathbb{R}$ will do the trick.

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[edit] Other mathematical fonts

It's possible to set a different font family for a complete mathematical expression.

\begin{align*}
3x^2 \in R \subset Q \\
\mathnormal{3x^2 \in R \subset Q} \\
\mathrm{3x^2 \in R \subset Q} \\
\mathit{3x^2 \in R \subset Q} \\
\mathbf{3x^2 \in R \subset Q} \\
\mathsf{3x^2 \in R \subset Q} \\
\mathtt{3x^2 \in R \subset Q} 
\end{align*}

In this case, not only letters but all characters change its appearance, for example $\mathit{3x^2}$ italicises the entire expression.

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[edit] Further reading

For more information see

• Mathematical expressions
• Subscripts and superscripts
• Bold, italics and underlining
• Font sizes, families, and styles
• Font typefaces
• Text alignment
• The not so short introduction to LaTeX2ε