How do we get Theorem environments without dot after the number?

Question

The standard Theorem environments under amsthm has Theorem n. How can we have simply Theorem n and so no punctuation after n?

Answer 1

You find the default parameters at https://tex.stackexchange.com/a/17555/4427

\newtheoremstyle{plain}
  {\topsep}   % ABOVESPACE
  {\topsep}   % BELOWSPACE
  {\itshape}  % BODYFONT
  {0pt}       % INDENT (empty value is the same as 0pt)
  {\bfseries} % HEADFONT
  {.}         % HEADPUNCT
  {5pt plus 1pt minus 1pt} % HEADSPACE
  {}          % CUSTOM-HEAD-SPEC

Define your own theorem styles based on this. Example:

\documentclass{article}
\usepackage{amsthm}
\newtheoremstyle{plainnopunct}
  {\topsep}   % ABOVESPACE
  {\topsep}   % BELOWSPACE
  {\itshape}  % BODYFONT
  {0pt}       % INDENT (empty value is the same as 0pt)
  {\bfseries} % HEADFONT
  {}          % HEADPUNCT
  {5pt plus 1pt minus 1pt} % HEADSPACE
  {}          % CUSTOM-HEAD-SPEC
\newtheoremstyle{definitionnopunct}
  {\topsep}   % ABOVESPACE
  {\topsep}   % BELOWSPACE
  {\upshape}  % BODYFONT
  {0pt}       % INDENT (empty value is the same as 0pt)
  {\bfseries} % HEADFONT
  {}          % HEADPUNCT
  {5pt plus 1pt minus 1pt} % HEADSPACE
  {}          % CUSTOM-HEAD-SPEC
\theoremstyle{plainnopunct}
\newtheorem{theorem}{Theorem}
\theoremstyle{definitionnopunct}
\newtheorem{definition}[theorem]{Definition}
\begin{document}
\begin{theorem}
This is a theorem statement.
\end{theorem}
\begin{definition}
This is a \emph{definition}.
\end{definition}
\begin{theorem}[Attribution]
This is a theorem statement.
\end{theorem}
\end{document}