sweatpants vs sweat pants

sweatpants and sweat pants both are nouns.

Word	Noun	Adjective	Verb	Adverb
sweatpants	Yes	No	No	No
sweat pants	Yes	No	No	No

As nouns, sweatpants and sweat pants are synonyms defined as:

sweatpants and sweat pants: loose-fitting trousers with elastic cuffs; worn by athletes

sweatpants (noun)	sweat pants (noun)
loose-fitting trousers with elastic cuffs; worn by athletes	loose-fitting trousers with elastic cuffs; worn by athletes