A coregency is the situation where a monarchical position (such as prince, princess, king, queen, emperor or empress), normally held by only a single person, is held by two or more. It is to be distinguished from diarchies or duumvirates (such as ancient Sparta and Rome), and also from regencies where a single monarch (usually infant or incapacitated) has a seniority above a regent but exercises no power except legally holding the position of head of state.