jaw vs gnaw

jaw is a noun but gnaw is not a noun.

Word	Noun	Adjective	Verb	Adverb
jaw	Yes	No	Yes	No
gnaw	No	No	Yes	No

As verbs, gnaw is a hyponym of jaw; that is, gnaw is a word with a more specific, narrower meaning than jaw:

Other hyponyms of jaw include champ, chomp, champ, gum, mumble, chaw, crunch, munch.

jaw (noun)	gnaw (noun)
holding device consisting of one or both of the opposing parts of a tool that close to hold an object
the part of the skull of a vertebrate that frames the mouth and holds the teeth
the bones of the skull that frame the mouth and serve to open it; the bones that hold the teeth

jaw (verb)	gnaw (verb)
talk socially without exchanging too much information	become ground down or deteriorate
censure severely or angrily	bite or chew on with the teeth
talk incessantly and tiresomely
chew (food); to bite and grind with the teeth