crepuscle vs night

crepuscle and night both are nouns.

Word	Noun	Adjective	Verb	Adverb
crepuscle	Yes	No	No	No
night	Yes	No	No	No

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

crepuscle (noun)	night (noun)
the time of day immediately following sunset	darkness
	the time after sunset and before sunrise while it is dark outside
	a period of ignorance or backwardness or gloom
	the dark part of the diurnal cycle considered a time unit
	the time between sunset and midnight
	the period spent sleeping
	a shortening of nightfall