upside vs crest

upside and crest both are nouns.

Word	Noun	Adjective	Verb	Adverb
upside	Yes	No	No	No
crest	Yes	No	Yes	No

As nouns, crest is a hyponym of upside; that is, crest is a word with a more specific, narrower meaning than upside:

Other hyponyms of upside include crown, poll, crown, pate, poll, desktop, rooftop, tiptop.

upside (noun)	crest (noun)
the highest or uppermost side of anything	a showy growth of e.g. feathers or skin on the head of a bird or other animal
	(heraldry) in medieval times, an emblem used to decorate a helmet
	the center of a cambered road
	the top line of a hill, mountain, or wave
	the top or extreme point of something (usually a mountain or hill)

upside (verb)	crest (verb)
	reach a high point
	lie at the top of