appendage vs fin

appendage and fin both are nouns.

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

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

appendage: an external body part that projects from the body
fin: organ of locomotion and balance in fishes and some other aquatic animals

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

appendage (noun)	fin (noun)
a part that is joined to something larger	organ of locomotion and balance in fishes and some other aquatic animals
an external body part that projects from the body	a stabilizer on a ship that resembles the fin of a fish
a natural prolongation or projection from a part of an organism either animal or plant	one of a set of parallel slats in a door or window to admit air and reject rain
	a shoe for swimming; the paddle-like front is an aid in swimming (especially underwater)
	one of a pair of decorations projecting above the rear fenders of an automobile
	the cardinal number that is the sum of four and one

appendage (verb)	fin (verb)
	show the fins above the water while swimming
	propel oneself through the water in a finning motion
	equip (a car) with fins