sports car vs sport car

sports car and sport car both are nouns.

Word	Noun	Adjective	Verb	Adverb
sports car	Yes	No	No	No
sport car	Yes	No	No	No

As nouns, sports car and sport car are synonyms defined as:

sports car and sport car: a small low car with a high-powered engine; usually seats two persons

sports car (noun)	sport car (noun)
a small low car with a high-powered engine; usually seats two persons	a small low car with a high-powered engine; usually seats two persons