sweatpants vs trousers

sweatpants and trousers both are nouns.

Word	Noun	Adjective	Verb	Adverb
sweatpants	Yes	No	No	No
trousers	Yes	No	No	No

As nouns, trousers is a hypernym of sweatpants; that is, trousers is a word with a broader meaning than sweatpants:

sweatpants: loose-fitting trousers with elastic cuffs; worn by athletes
trousers: (usually in the plural) a garment extending from the waist to the knee or ankle, covering each leg separately

Other hypernyms of sweatpants include pair of trousers, pant.

sweatpants (noun)	trousers (noun)
loose-fitting trousers with elastic cuffs; worn by athletes	(usually in the plural) a garment extending from the waist to the knee or ankle, covering each leg separately