polo shirt vs sport shirt

polo shirt and sport shirt both are nouns.

Word	Noun	Adjective	Verb	Adverb
polo shirt	Yes	No	No	No
sport shirt	Yes	No	No	No

As nouns, polo shirt and sport shirt are synonyms defined as:

polo shirt and sport shirt: a shirt with short sleeves designed for comfort and casual wear

polo shirt (noun)	sport shirt (noun)
a shirt with short sleeves designed for comfort and casual wear	a shirt with short sleeves designed for comfort and casual wear