## Class files

In mathematical mode characters are spaced as if they were part of a single word, regardless of the actual space you insert. This article explains how to insert spaces of different lengths in mathematical mode.

# Introduction

Spacing in maths mode is useful in several situations, let's see an example:

Assume we have the next sets
$S = \{ z \in \mathbb{C}\, |\, |z| < 1 \} \quad \textrm{and} \quad S_2=\partial{S}$

As you see in this example, a mathematical text can be explicitly spaced by means of some special commands

# Spaces

The spacing depends on the command you insert, the example below contains a complete list of spaces and how they look like.

Spaces in mathematical mode.

\begin{align*}
f(x) =& x^2\! +3x\! +2 \\
f(x) =& x^2+3x+2 \\
f(x) =& x^2\, +3x\, +2 \\
f(x) =& x^2\: +3x\: +2 \\
f(x) =& x^2\; +3x\; +2 \\
f(x) =& x^2\ +3x\ +2 \\
\end{align*}

Check the reference guide for a description of the commands.

Note: to see a description of the  align*  environment see Aligning equations with amsmath

# Operators spacing

Spacing around operators and relations in math mode are governed by specific skip lengths:

•  \thinmuskip  (by default it is equal to 3 mu)
•  \medmuskip  (by default it is equal to 4 mu)
•  \thickmuskip  (by default it is equal to 5 mu)

\begin{align*}
3ax+4by=5cz\\
3ax<4by+5cz
\end{align*}

For relationnal operators, such as < , > and =, L a T e X establishes  \thickmuskip  space. But for binary operators such as +, - and x, the  \medmuskip  space is set. The difference is almost unnoticeable.

# User-defined binary and relational operators

You can force the spacing used in binary or relational operators, so you can define your own .

\begin{align*}
34x^2a \mathbin{\#} 13bc \\
34x^2a \mathrel{\#} 13bc
\end{align*}

The previous example sets a particular spacing before and after  #  by using  \mathrel  (relational) and  \mathbin  (binary) commands.

# Reference guide

Description of spacing commands

L a T e X code Description
 \quad  space equal to the current font size (= 18 mu )
 \,  3/18 of  \quad  (= 3 mu)
 \:  4/18 of  \quad  (= 4 mu)
 \;  5/18 of  \quad  (= 5 mu)
 \!  -3/18 of  \quad  (= -3 mu)
 \  (space after backslash!) equivalent of space in normal text
 \qquad  twice of  \quad  (= 36 mu)