Which bone is considered the lower jaw bone?

The mandible is considered the lower jawbone primarily because it is the only movable bone in the skull that plays a crucial role in both the structure and function of the jaw. It holds the lower teeth and allows for movements such as chewing and speaking through its ability to open and close. The mandible articulates with the temporal bone at the temporomandibular joint, enabling this movement.

In contrast, the maxilla is the upper jawbone and forms the upper part of the mouth and supports the upper teeth. The zygoma, or cheekbone, is situated laterally to the mandible and is not involved in jaw movements. The frontal bone is located at the forehead and does not play any role in jaw structure or function. Thus, the distinguishing factors of the mandible as the lower jawbone are its location, structural role, and functionality in the oral cavity.