# \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.

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