1. The skull of a vertebrate; especially, the part that covers, or encloses, the brain.
2. The upper portion of the skull, which protects the brain.

The bones of the cranium include the frontal, parietal (main side bone of the skull), occipital (back of head), temporal, sphenoid (wedge-shaped bone at the base of the skull), ethmoid (irregularly shaped, spongy bone that provides the floor of the front part of the skull) and the roof of the nose, lacrimal (tear gland), and nasal (nose) bones; the concha nasalis; and the vomer (triangular bone in the nasal septum or dividing wall within the nose).

3. Etymology: from about 1543, from Medieval Latin (Latin as written and spoken c.700-c.1500), "cranium"; from Greek kranion, "skull"; related to kara, "head". Primarily a reference to the bones which enclose the brain.