sciatic nerve vs nervus

sciatic nerve and nervus both are nouns.

Word	Noun	Adjective	Verb	Adverb
sciatic nerve	Yes	No	No	No
nervus	Yes	No	No	No

As nouns, nervus is a hypernym of sciatic nerve; that is, nervus is a word with a broader meaning than sciatic nerve:

sciatic nerve: arises from the sacral plexus and passes about halfway down the thigh where it divides into the common peroneal and tibial nerves
nervus: any bundle of nerve fibers running to various organs and tissues of the body

Other hypernyms of sciatic nerve include nerve.

sciatic nerve (noun)	nervus (noun)
arises from the sacral plexus and passes about halfway down the thigh where it divides into the common peroneal and tibial nerves	any bundle of nerve fibers running to various organs and tissues of the body