cardigan vs sweater

cardigan and sweater both are nouns.

Word	Noun	Adjective	Verb	Adverb
cardigan	Yes	No	No	No
sweater	Yes	No	No	No

As nouns, sweater is a hypernym of cardigan; that is, sweater is a word with a broader meaning than cardigan:

cardigan: knitted jacket that is fastened up the front with buttons or a zipper
sweater: a crocheted or knitted garment covering the upper part of the body

Other hypernyms of cardigan include jumper.

cardigan (noun)	sweater (noun)
knitted jacket that is fastened up the front with buttons or a zipper	a crocheted or knitted garment covering the upper part of the body
	a person who perspires