sweater vs polo-neck

sweater and polo-neck both are nouns.

Word	Noun	Adjective	Verb	Adverb
sweater	Yes	No	No	No
polo-neck	Yes	No	No	No

As nouns, polo-neck is a hyponym of sweater; that is, polo-neck is a word with a more specific, narrower meaning than sweater:

Other hyponyms of sweater include cardigan, pullover, slipover, turtle, turtleneck.

sweater (noun)	polo-neck (noun)
a crocheted or knitted garment covering the upper part of the body	a sweater or jersey with a high close-fitting collar
a person who perspires