\newtheorem{env_name}{caption}[within] \newtheorem{env_name}[numbered_like]{caption}

This command defines a theorem-like environment.

  • env_name The name of the environment -- a string of letters. Must not be the name of an existing environment or counter.
  • caption The text printed at the beginning of the environment, right before the number.
  • within The name of an already defined counter, usually of a sectional unit. Provides a means of resetting the new theorem counter within the sectional unit.
  • numbered_like The name of an already defined theorem-like environment.

The \newtheorem command may have at most one optional argument.