tract vs white matter

tract and white matter both are nouns.

Word	Noun	Adjective	Verb	Adverb
tract	Yes	No	No	No
white matter	Yes	No	No	No

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

tract: 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 tract include substantia alba.

tract (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
a system of body parts that together serve some particular purpose
a brief treatise on a subject of interest; published in the form of a booklet
an extended area of land