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Often in physics, the symbol \sim is used as a unary operator to mean "approximately."

For example, one might say "the energy of these processes is $\sim 4$ eV." However, this looks awkward because \sim is a binary operator and the spacing is incorrect. How can one use \sim act as a unary operator?

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${\sim}4$ or $\mathord{\sim}4$ – Werner Oct 25 '12 at 21:31
\sim is a relation symbol, rather than a binary operation; if it were then $\sim 4$ would give no space. It's probably better to define a new command for it as an "Ord": \newcommand{\appx}{{\sim}}. Consider using siunitx for typesetting units of measure. – egreg Oct 25 '12 at 21:34
This question is a duplicate of tex.stackexchange.com/q/55701 – Philippe Goutet Oct 26 '12 at 5:30
up vote 10 down vote accepted

Just define a new command for it:


I suggest also to use siunitx, if you have units of measure to typeset in your document: it ensures uniform setting.



\SI{\ca 4}{eV}

$\ca 4$\,eV

The input might seem more difficult, but it's surely rewarding.

enter image description here

If you load amssymb you can change the definition to


and the result would be

enter image description here

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