# Typesetting for two variables muliplication

c, C, a, A are mathematical variables. $cC$ but the spacing is too close. The small c and big C almost stick together. How to solve this situation?

For example: $aA$ the spacing is ok.

• Play around with any of the suggestions in What commands are there for horizontal spacing? – Werner May 22 '15 at 18:40
• Use commutativity or ask the font maintainer to correct the kerning of this very character pair. – LaRiFaRi May 22 '15 at 18:48
• \newcommand*\cC{c\mspace{<whatever amount in mu>}C} That way you input it in a clear way, you can search & replace easily in your document, and you have control over the spacing in the whole document. – Manuel May 22 '15 at 22:48

It happens that certain combination of letters have “bad” spacing. This can happen more frequently in math mode, because different rules for kerning are used than in text mode. For Computer Modern, the kerning pairs have been defined by Knuth in a very careful way; however, due to the different rules used in math mode, less frequent combinations can lead to clashes.

In this case manual correction is needed:

\documentclass{article}
\usepackage{amsmath}

\begin{document}

$cC$ $aA$\par
$c\mspace{0.5mu}C$ $aA$\par
$c\mspace{1mu}C$ $aA$\par
$c\mspace{1.5mu}C$ $aA$\par
$c\mspace{2mu}C$ $aA$\par

\end{document}


Decide yourself what's the best for you.

• Is there any way to define additional math-mode kerning rules in the document preamble or in a separate package by using some hook or anything like this? Throughout a large document, manual corrections tend to be cumbersome and inconsistent. – Matthias Nov 22 '17 at 23:12
• @Matthias No, it's not possible. – egreg Nov 22 '17 at 23:21

you can try to space manually with $c\, C$ for a little space, you can also try with \: or \;.

Those are for small, medium or normal math space reciprocally.

Bye

The way to have the most control over the spacing is to use the \kern command:

$c\kern.125ex C$


Make sure to always define kerning commands relative to the font size using em or ex units, do not use in or cm.

If this is a kerning pair you'll be using a lot, you can define a command to make it easier and consistent throughout your document:

\newcommand{\cC}{c\kern.125ex C}


Now you can type \cC to get the properly kerned pair everywhere in your text.