nerve pathway vs white matter

nerve pathway and white matter both are nouns.

Word	Noun	Adjective	Verb	Adverb
nerve pathway	Yes	No	No	No
white matter	Yes	No	No	No

As nouns, white matter is a hypernym of nerve pathway; that is, white matter is a word with a broader meaning than nerve pathway:

nerve pathway: a bundle of myelinated nerve fibers following a path through the brain
white matter: whitish nervous tissue of the CNS consisting of neurons and their myelin sheaths

Other hypernyms of nerve pathway include substantia alba.

nerve pathway (noun)	white matter (noun)
a bundle of myelinated nerve fibers following a path through the brain	whitish nervous tissue of the CNS consisting of neurons and their myelin sheaths