amsthm

amsthm - Typesetting theorems (AMS style). The package facilitates the kind of theorem setup typically needed in American Mathematical Society publications. The package offers the theorem setup of the AMS document classes (amsart, amsbook, etc.) encapsulated in LATEX package form so that it can be used with other document classes. Amsthm is part of the (required) AMS-LATEX distribution, so should be present in any LATEX distribution.