Quadrumvirates are a group of four people who hold power or authority in an organization. Synonyms for quadrumvirates include quartet, foursome, quadrangle, quadruplet, tetrad, and fourfold. A quartet refers to a group of four musicians, singers, or performers, while a foursome refers to a group of four players in a game or sport. Quadrangle refers to a square courtyard surrounded by buildings, while a quadruplet refers to four babies born at the same time. Tetrad is a scientific term that describes a group of four closely related genes or chromosomes. Fourfold implies an increase or multiplication by four.