\newtheorem

LaTeX2e help 1.6

### 2.3.3: \newtheorem

       \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 to be defined. A string of letters. It 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. This may simply say ``Theorem'', for example.
`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.