upper jaw vs maxilla

upper jaw and maxilla both are nouns.

Word	Noun	Adjective	Verb	Adverb
upper jaw	Yes	No	No	No
maxilla	Yes	No	No	No

As nouns, upper jaw and maxilla are synonyms defined as:

upper jaw and maxilla: the jaw in vertebrates that is fused to the cranium

Other synonyms of upper jaw include maxillary, upper jawbone.

upper jaw (noun)	maxilla (noun)
the jaw in vertebrates that is fused to the cranium	the jaw in vertebrates that is fused to the cranium