Acetabulum

The acetabulum is the concave articular surface of the pelvis, formed by the parts of three bones, the ilium, ischium , and pubis . The head of the femur articulates with the pelvis at the acetabulum, forming the hip joint. In reptiles and in birds, the acetabulum are deep sockets. It has its counterpart in the pectoral girdle, namely, glenoid fossa .

The word acetabulum means "little vinegar cup."