pants vs knickers

pants and knickers both are nouns.

Word	Noun	Adjective	Verb	Adverb
pants	Yes	No	No	No
knickers	Yes	No	No	No

As nouns, pants and knickers are synonyms defined as:

Other synonyms of pants include bloomers, drawers.

pants (noun)	knickers (noun)
(used in the plural) underpants worn by women	(used in the plural) underpants worn by women
	(used in the plural) trousers ending above the knee