定义标题中的换行符（定理包）

Question

我在定理环境中遇到了行太长的问题。以下示例显示了这个问题，我需要在标题中换行，但没有。有什么建议吗？

\documentclass[a4paper,10pt,twocolumn]{article}

\usepackage{theorem}
{\theoremheaderfont{\upshape\bfseries}
 \theorembodyfont{\normalfont\slshape}
 \newtheorem{definition}{Definition}}

\begin{document}

\begin{definition}[Long heading that should have a line break]
A definition is a statement of the meaning of a term (a word, phrase, or other set of symbols).
Definitions can be classified into two large categories, intensional definitions (which try to give the essence of a term) and extensional definitions (which list every single object that a term describes).
A term may have many different senses and multiple meanings, and thus require multiple definitions.
\end{definition}

\end{document}

感谢您的帮助！

Answer 1

在另一个主题的帮助下，我自己找到了一个解决方案，如果有人感兴趣，解决方案如下。我将包“theorem”替换为“ntheorem”，并添加了一些形成命令，这些命令是我从另一个主题改编而来的：

\documentclass[a4paper,10pt,twocolumn]{article}

\usepackage{ntheorem}

\makeatletter
\renewtheoremstyle{plain}% Adds automatic line break, if heading is too long
  {\item{\theorem@headerfont ##1\ ##2\theorem@separator}~}
  {\item{\theorem@headerfont ##1\ ##2\ (##3)\theorem@separator}~}
\makeatother

{\theoremheaderfont{\upshape\bfseries}
 \theorembodyfont{\normalfont\slshape}
 \newtheorem{definition}{Definition}}

\begin{document}

\begin{definition}[Long heading that should have a line break]
A definition is a statement of the meaning of a term (a word, phrase, or other set of symbols).
Definitions can be classified into two large categories, intensional definitions (which try to give the essence of a term) and extensional definitions (which list every single object that a term describes).
A term may have many different senses and multiple meanings, and thus require multiple definitions.
\end{definition}

\end{document}

注 1：某个版主能把这个问题标记为已解决吗？（或者如果这个问题不有趣，就删除它。）我不知怎么的一开始无法登录，所以我以访客身份问了这个问题，现在自己找到了解决方案。

注 2：此解决方案与论坛中已有的解决方案不同！此解决方案不适用于定理包和此解决方案需要另外八行代码，而且结果也不同（我不希望在标题之后或在标题内部有换行符）。