maxilla vs upper jawbone

maxilla and upper jawbone both are nouns.

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

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

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

Other synonyms of maxilla include maxillary, upper jaw.

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