turtleneck collar vs polo-neck collar

turtleneck collar and polo-neck collar both are nouns.

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

As nouns, turtleneck collar and polo-neck collar are synonyms defined as:

turtleneck collar and polo-neck collar: a high close-fitting turnover collar

turtleneck collar (noun)	polo-neck collar (noun)
a high close-fitting turnover collar	a high close-fitting turnover collar