cranial nerve vs nervus

cranial nerve and nervus both are nouns.

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

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

cranial nerve: any of the 12 paired nerves that originate in the brain stem
nervus: any bundle of nerve fibers running to various organs and tissues of the body

Other hypernyms of cranial nerve include nerve.

cranial nerve (noun)	nervus (noun)
any of the 12 paired nerves that originate in the brain stem	any bundle of nerve fibers running to various organs and tissues of the body