sacrum – a triangular bone at the base of the spine

(Pronounced sac-rum)

To remember the meaning of sacrum, use the following mnemonic:

He was carrying a sack of rum (sacrum) over his back that hung at the base of his spine.

The sacrum is a large, triangular bone located at the base of the spine, formed by the fusion of five individual vertebrae that occurs during late adolescence and early adulthood. This wedge-shaped bone sits between the lumbar vertebrae above and the coccyx (tailbone) below. The sacrum also forms part of the pelvic girdle between the hip bones. It plays a key role in supporting the weight of the upper body and transmitting forces from the spine to the pelvis and legs during standing, walking and other weight-baring activities. Ligaments and muscles that attach to the sacrum help maintain pelvic stability and strength when lifting or bending. 

In females, the sacrum is typically shorter and wider than in males, which is an adaptation that helps accommodate childbirth by providing a larger pelvic outlet.