[Tex/LaTex] Typesetting \prime vs ‘

math-modesymbols

I'm trying to figure out how to best typeset primed values. It seems that, e.g.

$f'$ and $f\prime$ give off a slightly different result:

I like the right ( $a\prime$ ) version better, but I'm not sure if that's correct.

EDIT after going over my preamble, I found the "culprit" – it was the package unicode-math, which I added to be able to use \Colon. After removing it, my primes rendered exactly like in Mico's answer.

Best Answer

It seems that, e.g. $f'$ and $f\prime$ give off a slightly different result

First off, the item on the left-hand side of the screenshot you posted does not appear to have been created by either $f'$ and $f\prime$ -- at least not by either TeX or LaTeX. See also the screenshot below and the associated LaTeX code.

The item on the right-hand side could have been created by either $f'$ or $f^{\prime}$ , since the two methods are entirely equivalent.

In math mode, x' and x^{\prime} are equivalent. The former is a lot easier to type, though. This becomes especially evident for higher-order derivatives: Speaking for myself, I'd much rather type $f'''$ than $f^{\prime\prime\prime}$ .

\documentclass{article}
\begin{document}    
$f' \quad f^{\prime} \quad f\prime$ 
\end{document}

Related Solutions

[Tex/LaTex] Why isn’t \prime automatically set to be a superscript

This is actually one of the exercises in The TeXBook :) (exercise 16.5, p. 130):

Why do you think TeX treats \prime as a large symbol that appears only in superscripts, instead of making it a smaller symbol that has already been shifted up into the superscript position?

And the answer is:

The second alternative doesn’t work properly when there’s a subscript at the same time as a prime. Furthermore, some mathematicians use \prime also in the subscript position; they write, for example, $F'(w,z)=\partial F(w,z)/\partial z$ and $F_\prime(w,z)=\partial F(w,z)/\partial w$ .

[Tex/LaTex] Prime in text mode

If you really want the math prime symbol you may simply use $'$ or $\prime$ , or if you want to use it in text and math mode \ensuremath{'} or \ensuremath{\prime}, e.g.:

\documentclass{article}
\newcommand*{\everymodeprime}{\ensuremath{\prime}}
\begin{document}
Prime in text mode: \everymodeprime

Prime in math mode: $\everymodeprime$
\end{document}

I've used \prime instead of ' to avoid typo mistakes.

\ensuremath does only switch to math mode, if math mode it not already active. So it is often useful to define commands, that uses math mode commands and should work in text and math mode.

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Related Solutions

[Tex/LaTex] Why isn’t \prime automatically set to be a superscript

[Tex/LaTex] Prime in text mode

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