nervus vs fasciculus

nervus and fasciculus both are nouns.

Word	Noun	Adjective	Verb	Adverb
nervus	Yes	No	No	No
fasciculus	Yes	No	No	No

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

nervus: any bundle of nerve fibers running to various organs and tissues of the body
fasciculus: a bundle of fibers (especially nerve fibers)

Other hypernyms of nervus include fascicle, fiber bundle, fibre bundle.

nervus (noun)	fasciculus (noun)
any bundle of nerve fibers running to various organs and tissues of the body	a bundle of fibers (especially nerve fibers)