The hip socket is called the acetabulum; the hip bone is called the pelvis or pelvic girdle. The joint is the femoro-acetabular or femoro-pelvic joint.

Femur (thigh bone) fits into acetabulum.

acetabulum
acetabulum

The acetabulum is a concave surface of the pelvis. The head of the femur meets with the pelvis at the acetabulum, forming the hip joint

The acetabulum is the socket of the hip joint. In patient's with Marfan, the acetabulum becomes deeper than normal during growth, for reasons that are not yet understood.