Which human bone is the only one not directly connected to another bone?

The hyoid bone is the only human bone not directly connected to another bone. It lies in the front of the neck between the lower jaw and the larynx.

Instead of forming a conventional joint, the hyoid is suspended by muscles and ligaments. It supports the tongue and provides attachment points for muscles involved in swallowing, speaking, and movements of the floor of the mouth.

The hyoid has a distinctive U shape and is made of a body, two greater horns, and two lesser horns. It is sometimes confused with the larynx because both are in the throat, but the hyoid is a bone while the larynx is a cartilage-supported organ. Its unusual suspension gives the tongue and throat room to move.