atlas vs atlas vertebra

atlas and atlas vertebra both are nouns.

Word	Noun	Adjective	Verb	Adverb
atlas	Yes	No	No	No
atlas vertebra	Yes	No	No	No

As nouns, atlas and atlas vertebra are synonyms defined as:

atlas (noun)	atlas vertebra (noun)
a figure of a man used as a supporting column	the 1st cervical vertebra
the 1st cervical vertebra
a collection of maps in book form