The ilium or hipbone is a crucial component of the human skeletal system. It joins with the ischium and pubis bones to form the pelvis, which provides stability to the spine. There are several synonyms for the ilium or hipbone, including the coxa, innominate bone, and os coxae. The term coxa is commonly used in the medical field to refer to the hip joint. The innominate bone, on the other hand, is a term used to describe a bone with unknown or unclear origin. This term is used because the ilium bone is formed from three separate bones that fuse together during development. Finally, the term os coxae translates to "hip bone" in Latin and is commonly used in anatomy textbooks.