commissure vs tract

commissure and tract both are nouns.

Word	Noun	Adjective	Verb	Adverb
commissure	Yes	No	No	No
tract	Yes	No	No	No

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

commissure: a bundle of nerve fibers passing from one side to the other of the brain or spinal cord
tract: a bundle of myelinated nerve fibers following a path through the brain

Other hypernyms of commissure include nerve pathway, nerve tract, pathway.

commissure (noun)	tract (noun)
a bundle of nerve fibers passing from one side to the other of the brain or spinal cord	a bundle of myelinated nerve fibers following a path through the brain
	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