spa vs health spa

spa and health spa both are nouns.

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

As nouns, spa and health spa are synonyms defined as:

spa and health spa: a place of business with equipment and facilities for exercising and improving physical fitness

Other synonyms of spa include health club.

spa (noun)	health spa (noun)
a fashionable hotel usually in a resort area	a place of business with equipment and facilities for exercising and improving physical fitness
a place of business with equipment and facilities for exercising and improving physical fitness
a health resort near a spring or at the seaside