night vs nighttime

night and nighttime both are nouns.

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

As nouns, night and nighttime are synonyms defined as:

night and nighttime: the time after sunset and before sunrise while it is dark outside

Other synonyms of night include dark.

night (noun)	nighttime (noun)
darkness	the time after sunset and before sunrise while it is dark outside
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