short pants vs trousers

short pants and trousers both are nouns.

Word	Noun	Adjective	Verb	Adverb
short pants	Yes	No	No	No
trousers	Yes	No	No	No

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

short pants: (used in the plural) trousers that end at or above the knee
trousers: (usually in the plural) a garment extending from the waist to the knee or ankle, covering each leg separately

Other hypernyms of short pants include pair of trousers, pant.

short pants (noun)	trousers (noun)
(used in the plural) trousers that end at or above the knee	(usually in the plural) a garment extending from the waist to the knee or ankle, covering each leg separately