The term 'Ilium' refers to the uppermost and widest of the three bones that make up the human HIPBONE. It is also known as the 'os coxae' or 'hip bone'. The Ilium is connected to the sacrum and the pubis, forming the acetabulum, which is the socket that holds the head of the femur. In addition, the Ilium is the site of attachment for many muscles and ligaments. In Greek mythology, the city of TROY was said to have been founded on the Ilium, making it an important part of the story.