5

I want to change the font of the number to \itshape, for example, I want to get Theorem {\itshape 1.1}. Is there any way to do it in the theorem environment

5

Supposing you are only using the amsthm package in your document, this is how it can be done.

If you want this behavior only for the "plain" theorem style, add the following lines in your preamble to re-define the plain style:

\makeatletter
\renewcommand{\th@plain}{%
  \renewcommand\@upn{\textit}%
  \itshape%
}
\makeatother

and you're done.

MWE

\documentclass{article}
\usepackage{amsthm}

\makeatletter
\renewcommand{\th@plain}{%
  \renewcommand\@upn{\textit}%
  \itshape%
}
\makeatother

\newtheorem{thm}{Theorem}[section]

\begin{document}

\section{Test}

\begin{thm}
This is a theorem.
\end{thm}

\end{document} 

Output

enter image description here

Instead, if you want this behavior for all theorem styles, replace the above code with

\makeatletter
  \renewcommand\@upn{\textit}
\makeatother

MWE

\documentclass{article}
\usepackage{amsthm}

\makeatletter
  \renewcommand\@upn{\textit}
\makeatother

\newtheorem{thm}{Theorem}[section]
\theoremstyle{remark}
\newtheorem{rmk}[thm]{Remark}

\begin{document}

\section{Test}

\begin{thm}
This is a theorem.
\end{thm}

\begin{rmk}
And this is a remark.
\end{rmk}

\end{document} 

Output

enter image description here

3

Here is a way with ntheorem package. I redefine the plain style:

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage[amsthm, thmmarks, thref]{ntheorem}
\usepackage{cleveref}

\makeatletter
\renewtheoremstyle{plain}%
{\item[\hskip\labelsep \theorem@headerfont ##1\ \textit{##2}\theorem@separator]}%
{\item[\hskip\labelsep \theorem@headerfont ##1\ \textit{##2}\ (##3)\theorem@separator]}
\makeatother
\newtheorem{thm}{Theorem}[section]

\begin{document}

\section{A first section}
\begin{thm}\label{testthm}
This is a test theorem.
\end{thm}
We see in \cref{testthm}…

\end{document} 

enter image description here

3

If you're using no package specialized in theorems, you can do

\documentclass{article}
\usepackage{etoolbox}

\makeatletter
\patchcmd{\@opargbegintheorem}{#2}{\textit{#2}}{}{}
\patchcmd{\@begintheorem}{#2}{\textit{#2}}{}{}
\makeatother

\newtheorem{thm}{Theorem}

\begin{document}
\begin{thm}
Something
\end{thm}
\end{document}

enter image description here

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.