\newenvironment{nam}[args]{begdef}{enddef}
\newenvironment{nam}[args][default]{begdef}{enddef}
\renewenvironment{nam}[args]{begdef}{enddef}
These commands define or redefine an environment.
nam
\newenvironment there must be
no currently defined environment by that name, and the command
\nam must be undefined. For \renewenvironment the
environment must already be defined.
args
default
default
gives the default value for that argument.
begdef
\begin{nam}; a
parameter of the form #n in cmd is replaced by the text of
the nth argument when this substitution takes place.
enddef
\end{nam}. It may
not contain any argument parameters.
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