top vs crest

top and crest both are nouns.

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

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

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

As nouns, top and crest are synonyms defined as:

top and crest: the top or extreme point of something (usually a mountain or hill)

Other synonyms of top include crown, peak, summit, tip.

top (noun)	crest (noun)
a garment (especially for women) that extends from the shoulders to the waist or hips	a showy growth of e.g. feathers or skin on the head of a bird or other animal
covering for a hole (especially a hole in the top of a container)	(heraldry) in medieval times, an emblem used to decorate a helmet
a canvas tent to house the audience at a circus performance	the center of a cambered road
a conical child's plaything tapering to a steel point on which it can be made to spin	the top line of a hill, mountain, or wave
platform surrounding the head of a lower mast	the top or extreme point of something (usually a mountain or hill)
the greatest possible intensity
the highest or uppermost side of anything
the upper part of anything
the top or extreme point of something (usually a mountain or hill)
the highest level or degree attainable; the highest stage of development
the first half of an inning; while the visiting team is at bat

top (adjective)	crest (adjective)
situated at the top or highest position

top (verb)	crest (verb)
be the culminating event	reach a high point
finish up or conclude	lie at the top of
cut the top off
strike (the top part of a ball in golf, baseball, or pool) giving it a forward spin
pass by, over, or under without making contact
reach or ascend the top of
provide with a top or finish the top (of a structure)
be superior or better than some standard
be at the top of or constitute the top or highest point
be ahead of others; be the first