appendage vs limb

appendage and limb both are nouns.

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

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

appendage: an external body part that projects from the body
limb: one of the jointed appendages of an animal used for locomotion or grasping: arm, leg, wing, flipper

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

appendage (noun)	limb (noun)
a part that is joined to something larger	any projection that is thought to resemble a human arm
an external body part that projects from the body	the graduated arc that is attached to an instrument for measuring angles
a natural prolongation or projection from a part of an organism either animal or plant	either of the two halves of a bow from handle to tip
	one of the jointed appendages of an animal used for locomotion or grasping: arm, leg, wing, flipper
	(astronomy) the circumferential edge of the apparent disc of the sun or the moon or a planet
	any of the main branches arising from the trunk or a bough of a tree