backyard vs grounds

backyard and grounds both are nouns.

Word	Noun	Adjective	Verb	Adverb
backyard	Yes	No	No	No
grounds	Yes	No	No	No

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

Other hypernyms of backyard include curtilage, yard.

backyard (noun)	grounds (noun)
the grounds in back of a house	the enclosed land around a house or other building
	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