polo-neck collar vs neckband

polo-neck collar and neckband both are nouns.

Word	Noun	Adjective	Verb	Adverb
polo-neck collar	Yes	No	No	No
neckband	Yes	No	No	No

As nouns, neckband is a hypernym of polo-neck collar; that is, neckband is a word with a broader meaning than polo-neck collar:

Other hypernyms of polo-neck collar include collar.

polo-neck collar (noun)	neckband (noun)
a high close-fitting turnover collar	a band that fits around the neck and is usually folded over
	necklace that fits tightly around a woman's neck
	a band around the collar of a garment