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I was wondering whether it is possible to add some comment on top of the \approx symbol in a similar way that the command \xrightarrow{text} produces an arrow with text over it.

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3 Answers 3

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23

You can use the \stackrel{}{} for this:

\documentclass[preview]{standalone}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}
\newcommand{\approxtext}[1]{\ensuremath{\stackrel{\text{#1}}{\approx}}}
\begin{document}
    $\displaystyle
        A \stackrel{\text{text}}{\approx} B
    $, 
    $\displaystyle
        A \approxtext{test} B
    $
\end{document}

Or a small wrapper: \newcommand{\approxtext}[1]{\ensuremath{\stackrel{\text{#1}}{\approx}}}. Result:

enter image description here

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  • The text above the symbol should probably treated as text, not as math. What's the purpose of the additional braces?
    – egreg
    Mar 15, 2013 at 10:33
  • Thanks for such a detailed explanation However, I don't see the difference between the different approaches? I found that I can also accommodate math in the text above by the usual prescription $mathtext$
    – pablo
    Mar 15, 2013 at 10:54
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You can use \stackrel{a=b}{\approx} or if it is real text \stackrel{\text{your text}}{\approx} if your text is not too long. The \approx symbol is rather small, so I wouldn't add too much on top to keep your equations readable.

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  • That's working perfect! Thanks for the quickness! Just to know, which package does it comes from this? ams math?
    – pablo
    Mar 15, 2013 at 10:53
  • 1
    @pablo: Actually, you don't even need amsmath for this. But amsmath has two more commands: \overset and \underset. The former does basically the same as \stackrel
    – Anke
    Mar 15, 2013 at 11:13
  • What is the text is long? What command is to be used then?
    – user82588
    Nov 27, 2015 at 18:56
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As already mentioned \stackrel can be used for it. I'd just recommend adding \scriptscriptstyle or, say, \tiny if it is just text, plus \smash. Otherwise one often ends up having a combined symbol that mess with the line spacing if used in the text.

\newcommand\defeq{\stackrel{\smash{\scriptscriptstyle\mathrm{def}}}{=}}

Small size to reduce the height
\smash to remove the height completely (the small size then help us not to overlap too much with the line above)

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