tank suit vs swimwear

tank suit and swimwear both are nouns.

Word	Noun	Adjective	Verb	Adverb
tank suit	Yes	No	No	No
swimwear	Yes	No	No	No

As nouns, swimwear is a hypernym of tank suit; that is, swimwear is a word with a broader meaning than tank suit:

Other hypernyms of tank suit include bathing costume, bathing suit, swimming costume, swimsuit.

tank suit (noun)	swimwear (noun)
a woman's one-piece bathing suit	tight fitting garment worn for swimming