# How to get the closing single quote in math mode

How to get the closing single quote in math mode. The apostrophe in math mode is displayed as prime.

\documentclass{article}
\begin{document}
Why can't I get $a'$ in math mode.
\end{document}


You should switch to text-mode, eg.

\documentclass{article}
\begin{document}
Why can't I get $a\textrm'$ in math mode
\end{document}

• I find it is quite a good fix, but one caveat: for some formats you may get inconsistent results. For example, \boldmath $a\textrm'$shows the left quote bold, but the second not, because the second is set to standard roman. Just be aware. ;) By the way, egreg's solutions behaves correctly. Aug 13 '20 at 12:54

Punctuation that is not part of a formula should go outside the formula:

When $$a>0$$, we say that $$a$$ is \emph{positive}.

In the interval $$[0,1]$$ there are infinitely many rational numbers.


It's quite rare that quotes are used as math symbols, but I've seen them in some textbook on mathematical logic. Since ' is used for denoting a prime (dash) in math, one can resort to a different trick: the lines

\DeclareMathSymbol{\mlq}{\mathord}{operators}{}
\DeclareMathSymbol{\mrq}{\mathord}{operators}{'}


will define two commands that will give left and right quotes in math and your input can become

Why can't I get $\mlq a\mrq$ in math mode.


but in this case $a$' should be probably better.

I've added a companion to \mrq just for symmetry and, perhaps, greater clarity.

For the sake of completeness. A very flexible method to edit your equations is to step into text mode using the amsmath package command \text{<your text>}. Note that inside the \text command you can open new math environments. For example in the most simple case we might write: $\text{$a$'}$ .

Admittedly, it looks a bit awkward, but in the example below it feels acceptable.

I also compare the \text solution with the \mathrm solution: \mathrm uses always the roman family (serif), but the function \text adapts the quotes to the family that is being used at the moment, for example sans serif.

\documentclass{article}
\usepackage{amsmath}
\begin{document}

We have equation serif $$\text{a'}=20$$ $$a\textrm'=20$$
\sffamily We have equation sans $$\text{a'}=20$$ $$a\textrm'=20$$

\end{document}