provides a simple way to typeset the statements of
Theorems, Lemmas, Conjectures and so on. For each such type of
statement appearing in your text, you create an environment using
the \newtheorem command.
For example,
\newtheorem{prop}{Proposition}
sets up an environment named prop for typesetting
Propositions. After this command has been used, you can type
\begin{prop}
This is the text of my proposition.
\end{prop}
to get
Notice that the proposition was automatically numbered and typeset in italics.
A \newtheorem command can go anywhere in the file before the
first use of the environment it defines. For simplicity, it is
conventional to put it at the front of the file between the
\documentstyle line and
\begin{document}. (No text is allowed to appear
before \begin{document}, but commands like
\newtheorem, which generate no output, are permissible.)
You can give a theorem a name, or credit the discoverer, by giving
the \begin command an argument in square brackets. For
instance,
\newtheorem{thm}{Theorem}
\begin{thm}[Main Theorem]
This is the main theorem.
\end{thm}
produces
See Lamport's book for more details about
\newtheorem.