I apparently can't see the difference in a compilation (pdflatex) between \mathrm and \operatorname. So, as in the title the question is: is there a difference? Which one is preferable in what occasions?
3 Answers
There are many differences. The main one is in the fact that \mathrm{xyz} behaves like an ordinary letter, while \operatorname{xyz} behaves like function names such as \sin. Here's an illustration
$\sin x + \sin(x+y) + a\sin z$
$\mathrm{sin} x + \mathrm{sin}(x+y) + a\mathrm{sin}z$
where it's clear that the second line is typeset wrong. Even if your "operator" requires parentheses after it, it should be \operatorname, as the third summand shows, where a thin space separates the coefficient from the operator.
Another subtle difference is in how some characters are interpreted in \mathrm and in \operatorname. Suppose you have an operator to be called "pre-norm", with a hyphen. Here's the example
$\operatorname{pre-norm}(\mathbf{v})$
$\mathrm{pre-norm}(\mathbf{v})$
and now it's clear what is to be used. Indeed \operatorname (and the same holds for macros defined with \DeclareMathOperator) treats punctuation symbols in a special way; \mathrm, instead, treats them as math symbols.
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9Can you please tell the full form of the
rminmathrm? Thank you! Feb 14, 2018 at 5:12 -
19@GaurangTandon
rmstands for “roman”, that conventionally denotes the upright type used in the document.– egregFeb 14, 2018 at 8:59 -
1Wrapping
\mathrmwith\mathopaddresses the first point (spacing). Replacing\mathrmwith\textrmaddresses the second point (characters interpreted as math inside\mathrm{...}). So the next question is: what’s the difference between\mathop{\textrm{...}}and\operatorname{...}?– MaëlanMay 11, 2022 at 22:03 -
2@Maëlan Try
$\mathop{\textrm{xyz}}$inside a theorem statement typeset in italics.– egregMay 11, 2022 at 22:19
\operatorname:
The argument is written in upright mode but with some additional space before and behind.
\mathrm:
It is like math mode (no spaces), but in upright mode. The font size isn't changed.
The following example shows the differences:
\documentclass[]{article}
\usepackage{amsmath}
\begin{document}
\[x\operatorname{foo}y\]
\[x\mathrm{foo}y\]
\end{document}
answered Mar 18, 2012 at 9:48
In other LaTeX environments \mathrm{xyz} is useful. In MathJax v 2.0
$ i \\, \mathrm{sinh} \; $
gave the equivalent output as $ i \sinh x $. MathJax did not recognize \operatorname.
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15
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8Typo in the comment by @ChrisR (important if you're searching): it's AMSmath.js, (not ASMmath.js). Feb 14, 2020 at 20:24
\mathrmis used to make variables and units appear in roman (non-italic) text." - You can use it for units for example.