# Bold \varnothing

I'm using the symbol \varnothing and it turns out I could do with a bold version of it.

Any ideas?

Also, I'm using \phi as a 'lowercase' version of it, any improvements to this strategy would also be welcome.

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–  Andrew Swann May 12 '13 at 15:24
\varnothing isn't a letter that should be subject to upper/lower case. Can you not use \phi and \Phi ? –  David Carlisle May 12 '13 at 15:31
The idea of upper/lower case distinction might be applicable to symbols; many fonts contain upper and lower case versions of some punctuation characters, and a similar distinction is imaginable for operators, too. It’s really the bolding that raises the question “why?” Math expressions should normally not be bolded, since bolding of letters and some symbols may indicate difference in meaning (e.g., bold letters might denote vectors). So bolding as stylistic device should be avoided. –  Jukka K. Korpela May 12 '13 at 15:37
@JukkaK.Korpela The "why?" is very complicated, but let me assure you that I am aware of the stylistic and formal conventions of the fields to which my work belongs. –  Lucas May 12 '13 at 16:12
depending on the reason for wanting a bold version (as @JukkaK.Korpela says, it should be used only for a "mathematical" reason, not to harmonize with the style of a heading), the only way to get it with the ams "extra math symbols" is to use "poor man's bold" (\pmb{\varnothing}), since no bold version of these extra symbols was created; and that looks horrible. there is a bold version in the stix fonts, but i'll leave the details for someone else to answer. (the stix symbols don't always harmonize well with computer modern.) –  barbara beeton May 12 '13 at 16:15
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## 2 Answers

depending on the reason for wanting a bold version of \varnothing (as @JukkaK.Korpela says in a comment, it should be used only for a "mathematical" reason, not to harmonize with the style of a heading), the only way to get it with the ams "extra math symbols" is to use "poor man's bold" (\pmb{\varnothing}), since no bold version of these extra symbols was created. but that looks horrible.

there is a bold version in the stix fonts. some information on their use is given in an answer to this question: Is it already possible to use the STIX fonts? (note that the stix symbols don't always harmonize well with computer modern.)

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We can use another method to bold Greek letters and symbols that \mathbf doesn't work on, but this method doesn't work on \varnothing. However, it does work on \O and \emptyset.

\pmb was the only one to work on \varnothing but as barbara beeton pointed out it doesn't look that great. If you are okay with using \O or \emptyset, we can avoid the use of \pmb

\documentclass{article}
\usepackage{mathtools}
\usepackage{amssymb}
\newcommand{\bfs}[1]{\mbox{\boldmath$#1$}}
\begin{document}
\begin{alignat*}{4}
\varnothing & \qquad\bfs{\varnothing} & \qquad \mathbf{\varnothing}
& \qquad \pmb{\varnothing}\\
\phi & \qquad\bfs{\phi} & \qquad \mathbf{\phi} & \qquad \pmb{\phi}\\
\Phi & \qquad\bfs{\Phi} & \qquad \mathbf{\Phi} & \qquad \pmb{\Phi}\\
\O & \qquad\bfs{\O} & \qquad \mathbf{\O} & \qquad \pmb{\O}\\
\emptyset & \qquad\bfs{\emptyset} & \qquad \mathbf{\emptyset}
& \qquad \pmb{\emptyset}
\end{alignat*}
\end{document}


Close up of \pmb

Close up of \newcommand which didn't work on \varnothing but works on the rest.

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