\newenvironment

 

\newenvironment{nam}[args]{begdef}{enddef}  

\renewenvironment{nam}[args]{begdef}{enddef}

 

These commands define or redefine an environment.

Changes in LaTeX2e

 

It is possible to have an optional argument, the form of the command being
  \newenvironment{nam}[args][opt]{begdef}{enddef}
  \renewenvironment{nam}[args][opt]{begdef}{enddef}
If opt is present, the first of the args arguments is optional with default value opt. If it is absent all arguments are mandatory.

Related topics:

Defining commands, Environments