playground vs spa

playground and spa both are nouns.

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

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

playground: an area where many people go for recreation, holidays or other purposes
spa: a health resort near a spring or at the seaside

playground (noun)	spa (noun)
yard consisting of an outdoor area for children's play	a fashionable hotel usually in a resort area
an area where many people go for recreation, holidays or other purposes	a place of business with equipment and facilities for exercising and improving physical fitness
	a health resort near a spring or at the seaside