# Create a Circled Lowercase Omega

I need a circled \omega which looks and behaves like amssymb's \circledast. Here is what I have so far:

\documentclass[margin=2mm]{standalone}

\usepackage{amsmath}
\usepackage{amssymb}

\usepackage{tikz}

\newsavebox{\circledomegabox}
\savebox{\circledomegabox}{\tikz[baseline=-.75ex]{%
\node [shape=circle,draw,inner sep=0,scale=0.65] (char) {\ensuremath{\hspace*{0.2mm}\omega}};}}

\newcommand{\circledomega}{\makeatletter%
\def\c@rcled{\usebox{\circledomegabox}}%
\smash{\mathchoice{\text{\small\ensuremath{\c@rcled}}}%
{\text{\small\ensuremath{\c@rcled}}}%
{\text{\scriptsize\ensuremath{\c@rcled}}}%
{\text{\tiny\ensuremath{\c@rcled}}}}%
\makeatother}

\begin{document}

{\scriptsize $\circledomega$} $\Sigma^{\circledomega} \Sigma^\omega \Sigma^* \Sigma^\circledast$
$\displaystyle \Sigma^\omega \Sigma^{\circledomega} \Sigma^\circledast \Sigma^*$

\end{document}


As you can see, this approach has some problems:

1. The circled omega's baseline is not aligned to the baseline of the normal omega. Of course, I can adapt baseline= to get a better looking result. But is there a way to make it align automatically?
2. The circled omega is less bold than the normal one. Why is this and how can I fix it?
3. The circle's size and line weight to not match the one of \circledast. How can I determine their exact values?

Edit: As the question arose in one of the comments to egreg's answer: the symbol is only ever used in the context of \Sigma^\circledomega, so it is not too important how it looks in other contexts.

• baseline=char.base (from memory, not sure) – JLDiaz Oct 19 '15 at 13:15

## 3 Answers

One simple way is using amsmath:

\usepackage{amsmath}
\newcommand*{\circledomega}{\text{\textcircled{$\omega$}}}


A longer way is by means of \ooalign:

\documentclass{article}

\makeatletter
\newcommand*{\circledomega}{\mathpalette\@circledomega\relax}
\newcommand*{\@circledomega}[2]{%
\setbox0=\hbox{\m@th$#1\omega$}%
\setbox1=\hbox{\m@th$#1\bigcirc$}%
{\ooalign{\hfil\box0\hfil\cr\hfil\box1\hfil}}%
}
\makeatother

\begin{document}
${\displaystyle\circledomega\omega} {\textstyle\circledomega\omega} {\scriptstyle\circledomega\omega} {\scriptscriptstyle\circledomega\omega}$
\end{document}


I'm not sure I can help you with your point 3 though. The circle around \circledast is (in my opinion) too small for the \omega.

• I like the simplicity of your first solution. – JPW Oct 21 '15 at 8:19

Doing it the old way, by adapting the definition of \textcircled:

\documentclass{article}
\usepackage{amsmath,amssymb}

\makeatletter
\DeclareRobustCommand{\circledomega}{\text{\circled@omega}}

\newcommand{\circled@omega}{%
\hmode@bgroup\fontencoding{OMS}\selectfont
\vphantom{\char 13}%
\ooalign{%
\hfil\raise.07ex\hbox{$\m@th\omega$}\hfil\crcr
\char 13 % "0D
}%
\egroup}
\makeatother

\begin{document}

$\circledomega$ {\scriptsize $\circledomega$}
$\Sigma^{\circledomega} \Sigma^\omega \Sigma^* \Sigma^\circledast$
$\displaystyle \Sigma^\omega \Sigma^{\circledomega} \Sigma^\circledast \Sigma^*$

\end{document}


• somehow, that omega looks a bit large to me. at least, it increases the size of the circle. how that looks in context isn't entirely clear, since it isn't clear that the context shown is the only context in which it will be used. – barbara beeton Oct 19 '15 at 14:36
• @barbarabeeton I'm not really sure what the purpose is, actually. – egreg Oct 19 '15 at 14:37

Here is a stackengine approach. It will adapt to the current mathstyle

\documentclass{article}
\usepackage{amsmath,stackengine,scalerel}
\newcommand\circledomega{{\ThisStyle{\stackinset{c}{}{c}{}{$% \SavedStyle\omega$}{$\SavedStyle\bigcirc$}}}}
\newcommand\circledast{{\ThisStyle{\stackinset{c}{}{c}{}{$% \SavedStyle*$}{$\SavedStyle\bigcirc$}}}}
\begin{document}
{\scriptsize $\circledomega$} $\Sigma^{\circledomega} \Sigma^\omega \Sigma^* \Sigma^\circledast$
$\displaystyle \Sigma^\omega \Sigma^{\circledomega} \Sigma^\circledast \Sigma^*$

$\circledomega\circledast\scriptstyle \circledomega\circledast\scriptscriptstyle \circledomega\circledast$
\end{document}