Upright quote in equation

Question

What I want to have are single quotes in an equation which are just straight down like 'a'. It seems that the default is somewhat italic like ´a´.

I found lots of example to change the fontstyles inline of a text but they never affected the equation.

\begin{equation} sometext = 'abc' \end{equation}

produces:

sometext = ´abc´ (1)

I need :

sometext = 'abc' (1)

Answer 1

upquote and textcomp can help here:

\documentclass{article}

\usepackage{upquote,textcomp,amsmath}
\newcommand{\upquote}{\text{\textquotesingle}}

\begin{document}

\begin{equation}
   f(x) = \upquote abc \upquote
\end{equation}

\end{document}

Answer 2

The character ' is already taken for denoting, in math mode, a prime like in derivatives; in text mode it produces an apostrophe/right quote.

You can define a new math symbol font (if you have room for it}

\documentclass{article}
\usepackage{textcomp} % for TS1
\usepackage{amsmath}

\DeclareSymbolFont{textsymbols}{TS1}{\familydefault}{m}{n}
\SetSymbolFont{textsymbols}{bold}{TS1}{\familydefault}{m}{n}

\DeclareMathSymbol{\ulq}{\mathopen}{textsymbols}{39}
\DeclareMathSymbol{\urq}{\mathclose}{textsymbols}{39}

\begin{document}

\begin{equation}
f(x) = \log\ulq x \urq
\end{equation}

\end{document}

Otherwise a less efficient definition that spares a math group, but requires some more work for respecting \boldmath:

\documentclass{article}
\usepackage{textcomp} % for TS1
\usepackage{amsmath}

\newcommand{\ulq}{\mathopen{\textnormal{\textquotesingle}}}
\newcommand{\urq}{\mathclose{\textnormal{\textquotesingle}}}

\begin{document}

\begin{equation}
f(x) = \log\ulq x \urq
\end{equation}

\end{document}

If you want upright text in your equation:

\begin{equation}
\textnormal{sometext}=\ulq\textnormal{abc}\urq
\end{equation}

but this is a different thing than straight quotes.

Answer 3

have you tried this:

\begin{equation} \text{sometext} = \text{'abc'} \end{equation}