grounds vs playground

grounds and playground both are nouns.

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

As nouns, playground is a hyponym of grounds; that is, playground is a word with a more specific, narrower meaning than grounds:

Other hyponyms of grounds include backyard, dooryard, front yard, garden, side yard.

grounds (noun)	playground (noun)
the enclosed land around a house or other building	yard consisting of an outdoor area for children's play
your basis for belief or disbelief; knowledge on which to base belief	an area where many people go for recreation, holidays or other purposes
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