left field vs tract

left field and tract both are nouns.

Word	Noun	Adjective	Verb	Adverb
left field	Yes	No	No	No
tract	Yes	No	No	No

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

Other hypernyms of left field include parcel, parcel of land, piece of ground, piece of land.

left field (noun)	tract (noun)
the fielding position of the player on a baseball team who is expected to field balls in the left third of the outfield (looking from home plate)	a bundle of myelinated nerve fibers following a path through the brain
the piece of ground in the outfield on the catcher's left	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