extensor vs quadriceps

extensor and quadriceps both are nouns.

Word	Noun	Adjective	Verb	Adverb
extensor	Yes	No	No	No
quadriceps	Yes	No	No	No

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

extensor: a skeletal muscle whose contraction extends or stretches a body part
quadriceps: a muscle of the thigh that extends the leg

Other hyponyms of extensor include musculus quadriceps femoris, quad, quadriceps femoris.

extensor (noun)	quadriceps (noun)
a skeletal muscle whose contraction extends or stretches a body part	a muscle of the thigh that extends the leg