Regiment.

About Regiment

A regiment is a military unit that has been in use by the United States Army since its inception. Derived from the concept originating in European armies, a regiment was historically commanded by a colonel, and consisted of ten companies, for a total of approximately 1,000 soldiers. Confusingly, the terms "regiment" and "battalion" were used interchangeably at this time; it was not until later that a battalion was defined as a sub-unit of a regiment.