What is the lower portion of the pelvic bone called?

The lower portion of the pelvic bone is referred to as the ischium. This region plays a critical role in supporting the weight of the body when sitting and provides attachment points for various muscles and ligaments. The ischium forms part of the pelvic girdle and is located below the iliac bones and in front of the sacrum. Its structure includes the ischial tuberosities, which are the bony prominences that bear the weight when a person is seated.

In contrast, the pubis is situated at the front part of the pelvis and forms the pubic symphysis, while the ilium is the larger, uppermost bone of the pelvis, making it significant for overall pelvic structure. The femur, on the other hand, is the thigh bone and is not part of the pelvic bone structure itself, further clarifying why ischium is the appropriate answer.