prosthesis vs leg

prosthesis and leg both are nouns.

Word	Noun	Adjective	Verb	Adverb
prosthesis	Yes	No	No	No
leg	Yes	No	No	No

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

Other hyponyms of prosthesis include glass eye, implant, obturator, peg, pegleg, wooden leg, vascular conduit, vascular prosthesis.

prosthesis (noun)	leg (noun)
corrective consisting of a replacement for a part of the body	a section or portion of a journey or course
	(nautical) the distance traveled by a sailing vessel on a single tack
	a cloth covering consisting of the part of a pair of trousers that covers a person's leg
	one of the supports for a piece of furniture
	a prosthesis that replaces a missing leg
	a human limb; commonly used to refer to a whole limb but technically only the part of the limb between the knee and ankle
	a structure in animals that is similar to a human leg and used for locomotion
	the limb of an animal used for food
	a part of a forked or branching shape