Ntheorem：尽管有 \theoremstyle{definition}，定义仍以斜体显示

Question

我正在使用 ntheorem。我的定理中的文本按预期以斜体显示。但是，我的定义中的文本也是斜体，而这不应该。我在定义定义之前使用了 \theoremstyle{definition} 命令，但 PDF 的构建方式好像定理和定义都具有相同的定理样式。我怎样才能从我的定义中删除斜体？

\documentclass[twoside]{article} 
\usepackage{amssymb} 
\usepackage{amsmath}
\usepackage{mathtools}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\usepackage[amsmath, thmmarks, thref]{ntheorem}
\newtheorem{thm}{Theorem}[subsection]
\theoremstyle{definition}
\newtheorem{defin}[thm]{Definition}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\begin{document}
\section{Section Number One}
\begin{thm}
    I am glad that this is showing up in italics
\end{thm}

\begin{defin}
    Since I have used ``theoremstyle:definition'' in the header of my tex file, I am expecting this not to show up in italics.
\end{defin}

\end{document}

Answer 1

没有definition风格ntheorem。

\documentclass[twoside]{article}
\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{mathtools}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\usepackage[amsmath, thmmarks, thref]{ntheorem}
\newtheorem{thm}{Theorem}[subsection]

\theorembodyfont{\upshape}
\newtheorem{defin}[thm]{Definition}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\begin{document}
\section{Section Number One}
\begin{thm}
    I am glad that this is showing up in italics
\end{thm}

\begin{defin}
Since I have used ``theoremstyle:definition'' in the header 
of my tex file, I am expecting this not to show up in italics.
\end{defin}

\end{document}

您确定吗[subsection]？