grounds vs piece of land

grounds and piece of land both are nouns.

Word	Noun	Adjective	Verb	Adverb
grounds	Yes	No	No	No
piece of land	Yes	No	No	No

As nouns, piece of land is a hypernym of grounds; that is, piece of land is a word with a broader meaning than grounds:

grounds: a tract of land cleared for some special purposes (recreation or burial etc.)
piece of land: an extended area of land

Other hypernyms of grounds include parcel, parcel of land, piece of ground, tract.

grounds (noun)	piece of land (noun)
the enclosed land around a house or other building	an extended area of land
your basis for belief or disbelief; knowledge on which to base belief
a justification for something existing or happening
a tract of land cleared for some special purposes (recreation or burial etc.)
dregs consisting of solid particles (especially of coffee) that form a residue