grassland vs tract

grassland and tract both are nouns.

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

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

grassland: land where grass or grasslike vegetation grows and is the dominant form of plant life
tract: an extended area of land

Other hypernyms of grassland include biome, parcel, parcel of land, piece of ground, piece of land.

grassland (noun)	tract (noun)
land where grass or grasslike vegetation grows and is the dominant form of plant life	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