# How can I make the crossed-“O” ($\oslash$) bold?

I'd like to bolden the crossed-o but

\textbf{$\oslash$}


does nothing!

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\usepackage{bm} and $\bm{\oslash}$ should do. –  egreg May 26 '13 at 11:02
@mateuz Please, take a look at tex.stackexchange.com/questions/595/… –  Papiro May 26 '13 at 11:14
Please note that \oslash is not the same as the HTML-entity &oslash; (a.k.a. the Danish/Norwegian letter Ø), or the diameter symbol ⌀, or the empty set symbol ∅. –  kahen May 26 '13 at 11:23
\textbd{$\oslash$} will produce an "Undefined control sequence" error, so I guess you mean \textbf{$\oslash$}. –  lockstep May 26 '13 at 12:16
Kahen's comment is accurate. You shouldn't be using \oslash anyway, but rather just Ø, which you can do if you use UTF-8 as your file encoding. See the comments/answers to your other questions on this. –  Alan Munn May 26 '13 at 12:23

You can use the bm package to get bold math characters. See

How can I get bold math symbols?

However, for your actual purposes, (linguistics) you should not be using the math symbol \oslash anyway, but you should just use the regular upper case Ø, in which case it can be made boldface without any extra packages.

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But what package do I need to get "Ø"? Copy-and-pasting directly gives me Ã Ÿ –  Teusz Jul 15 '13 at 5:43
@mateuz You shouldn't need a package. How is your input file encoded? You should use latin1 or utf8 You need to load the inputenc package with the correct encoding specified (unless you're using XeTeX) You also need to make sure that you are loading a font that contains that the glyph (so \usepackage[T1]{fontenc} (again, unless you are using XeTeX)). If you took my other advice, you should be using XeTeX in which case your file must be encoded utf8 and things should just work. –  Alan Munn Jul 15 '13 at 12:41
Not sure how it's encoded (I'm using TextMate 4, not XeTeX), but even with \usepackage[T1]{fontenc}, I still get those two glypsh I mentioned above. –  Teusz Jul 15 '13 at 13:25

There are several options for obtaining bold characters in math mode. I have often read, that using the bm-package with \bm is the best practice, although I don't know why.

Implementation

\documentclass[border=3mm]{standalone}
\usepackage{amsmath}
\usepackage{bm}
\begin{document}
Options for bold $\oslash$:
$\boldsymbol{\oslash}$ vs.
{\boldmath $\oslash$} vs.
$\bm{\oslash}$
\end{document}


Output

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