cranium vs bone

cranium and bone both are nouns.

Word	Noun	Adjective	Verb	Adverb
cranium	Yes	No	No	No
bone	Yes	Yes	Yes	No

As nouns, bone is a hypernym of cranium; that is, bone is a word with a broader meaning than cranium:

Other hypernyms of cranium include os.

cranium (noun)	bone (noun)
the part of the skull that encloses the brain	a shade of white the color of bleached bones
	rigid connective tissue that makes up the skeleton of vertebrates
	the porous calcified substance from which bones are made

cranium (adjective)	bone (adjective)
	consisting of or made up of bone

cranium (verb)	bone (verb)
	remove the bones from
	study intensively, as before an exam