# Regular non-italic font in theorems

What can I do if I want a regular non-italic font character in the theorem environment? Neither text{} nor textit{} seem to work, and similar questions all ask about changing the style of the entire environment, not of just a few characters.

\newtheorem{theorem}{Theorem}[section]
\newtheorem{corollary}{Corollary}[theorem]
\newtheorem{lemma}[theorem]{Lemma}

• Welcome to TeX.SE! Please make your code snippet compilable! – Mensch Oct 24 '18 at 0:32

Here are a couple of options:

\documentclass{article}

\newtheorem{theorem}{Theorem}[section]

\begin{document}

\section{A section}

\begin{theorem}[Some theorem]
This is a theorem.
\emph{emph} or
\textup{textup} or
{\normalfont normalfont} or
\textnormal{textnormal}
This is the end of the theorem.
\end{theorem}

\end{document}