axis vertebra vs neck bone

axis vertebra and neck bone both are nouns.

Word	Noun	Adjective	Verb	Adverb
axis vertebra	Yes	No	No	No
neck bone	Yes	No	No	No

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

axis vertebra: the 2nd cervical vertebra; serves as a pivot for turning the head
neck bone: one of 7 vertebrae in the human spine located in the neck region

Other hypernyms of axis vertebra include cervical vertebra.

axis vertebra (noun)	neck bone (noun)
the 2nd cervical vertebra; serves as a pivot for turning the head	one of 7 vertebrae in the human spine located in the neck region