axis vs axis vertebra

axis and axis vertebra both are nouns.

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

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

axis and axis vertebra: the 2nd cervical vertebra; serves as a pivot for turning the head

axis (noun)	axis vertebra (noun)
the center around which something rotates	the 2nd cervical vertebra; serves as a pivot for turning the head
the 2nd cervical vertebra; serves as a pivot for turning the head
a straight line through a body or figure that satisfies certain conditions
a group of countries in special alliance
the main stem or central part about which plant organs or plant parts such as branches are arranged