This document discusses fair use in copyright law in the United States. It covers the concept of fair use and the four factors used to determine if a use is considered fair: (1) the purpose and character of the use, (2) the nature of the work, (3) the amount of the work used, and (4) the economic impact of the use. The document examines how these factors have been applied in various court cases involving parody, news reporting, and time-shifting of television programs.