Active describes a piece that commands a wide range of squares, threatens the opponent's position, or has significant mobility. An active piece controls key squares, participates in attacks, and can be deployed in combinations or tactical operations. In contrast to a passive piece, an active piece exerts influence beyond mere defence. Maximising piece activity is a fundamental principle of chess strategy—a well-placed knight on an outpost, a rook on an open file, or a bishop commanding a long diagonal are all examples of active pieces.