1.the time after sunset and before sunrise while it is dark outside
2.the time between sunset and midnight;
he watched television every night
3.the period spent sleeping;
I had a restless night
4.the dark part of the diurnal cycle considered a time unit;
three nights later he collapsed
5.darkness;
it vanished into the night
6.a shortening of nightfall;
they worked from morning to night
7.a period of ignorance or backwardness or gloom