mud flat vs tract

mud flat and tract both are nouns.

Word	Noun	Adjective	Verb	Adverb
mud flat	Yes	No	No	No
tract	Yes	No	No	No

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

mud flat: a tract of low muddy land near an estuary; covered at high tide and exposed at low tide
tract: an extended area of land

Other hypernyms of mud flat include parcel, parcel of land, piece of ground, piece of land.

mud flat (noun)	tract (noun)
a tract of low muddy land near an estuary; covered at high tide and exposed at low tide	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