member vs fin

member and fin both are nouns.

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

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

member: 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 member include chelicera, mouthpart, fang, chela, claw, nipper, pincer, parapodium, pleopod, swimmeret, limb, dactyl, digit.

member (noun)	fin (noun)
an external body part that projects from the body	organ of locomotion and balance in fishes and some other aquatic animals
the male sex organ	a stabilizer on a ship that resembles the fin of a fish
an organization that is a member of another organization (especially a state that belongs to a group of nations)	one of a set of parallel slats in a door or window to admit air and reject rain
one of the persons who compose a social group (especially individuals who have joined and participate in a group organization)	a shoe for swimming; the paddle-like front is an aid in swimming (especially underwater)
anything that belongs to a set or class	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

member (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