### 8.25 `theorem`

Synopsis:

\begin{theorem}
`theorem body`
\end{theorem}

Produces ‘`Theorem ``n`’ in boldface followed by `theorem
body` in italics. The numbering possibilities for `n` are described under
`\newtheorem`

(see `\newtheorem`

).

\newtheorem{lem}{Lemma} % in preamble
\newtheorem{thm}{Theorem}
...
\begin{lem} % in document body
text of lemma
\end{lem}
The next result follows immediately.
\begin{thm}[Gauss] % put `Gauss' in parens after theorem head
text of theorem
\end{thm}

Most new documents use the packages `amsthm`

and `amsmath`

from the American Mathematical Society. Among other things these
packages include a large number of options for theorem environments,
such as styling options.