coccyx /kok″siks/ pl. coccyges [Gk, kokkyx, cuckoo’s beak] , the beaklike bone joined to the sacrum by a disk of fibrocartilage at the base of the vertebral column. It is formed by the union of three to five probably vestigial rudimentary vertebrae. The pieces of the coccyx fuse together in males at an earlier period in life than in females. In both the coccyx becomes fused with the sacrum by the sixth decade of life. The coccyx is freely movable on the sacrum during pregnancy. −coccygeal, adj.
