# Beamer and Serif fonts

How does one specify a particular letter to be serif in the beamer class? I want to keep the notation as similar in the presentation as the article as I can, and most of it turns out well, except for the capital Greek letter phi. I found this question to achieve my goal (the letter looks like I want it to look, but the feel of the presentation has altered due to the serif font in math mode). As a result, I'm just trying to change the single letter.

If necessary, I can add a MWE, but it doesn't seem necessary to me at the moment.

• A MWE may not seem necessary to you, but think of the extra work it represents for TeX.SX users willing to give you a hand. Help them help you: remove that one hurdle between you and a solution to your problem. – user36296 Aug 30 '15 at 11:25
• So you want to change \phi back? Why not redefine \phi? – Symbol 1 Aug 30 '15 at 12:03

If you are using the default settings and want serif font for just a symbol, you can define a command for it using \mathrm

\documentclass{beamer}
\newcommand\SPi{\mathrm{\Pi}}

\begin{document}
\begin{frame}
$\SPi\quad\Pi$
\end{frame}
\end{document}


On the other hand, if you are using the serif math fonts, you can use \mathsf to define your sans-serif symbol:

\documentclass{beamer}
\usefonttheme[onlymath]{serif}
\newcommand\SPi{\mathsf{\Pi}}

\begin{document}
\begin{frame}
$\SPi\quad\Pi$
\end{frame}
\end{document}


Of course, you can also redefine the symbols (having previously made a copy):

\documentclass{beamer}

\let\oldPi\Pi
\renewcommand\Pi{\mathrm{\oldPi}}

\begin{document}
\begin{frame}
$\Pi\quad\oldPi$
\end{frame}
\end{document}