appendage vs mouthpart

appendage and mouthpart both are nouns.

Word	Noun	Adjective	Verb	Adverb
appendage	Yes	No	No	No
mouthpart	Yes	No	No	No

As nouns, mouthpart is a hyponym of appendage; that is, mouthpart is a word with a more specific, narrower meaning than appendage:

appendage: an external body part that projects from the body
mouthpart: any part of the mouth of an insect or other arthropod especially one adapted to a specific way of feeding

Other hyponyms of appendage include chelicera, fang, chela, claw, nipper, pincer, parapodium, fin, pleopod, swimmeret, limb, dactyl, digit.

appendage (noun)	mouthpart (noun)
a part that is joined to something larger	any part of the mouth of an insect or other arthropod especially one adapted to a specific way of feeding
an external body part that projects from the body
a natural prolongation or projection from a part of an organism either animal or plant