ETYM Old Eng. night, niht, as. neaht, niht.
(Homonym: knight).
1. The time after sunset and before sunrise while it is dark outside; SYN. nighttime, dark.
2. The time between sunset and midnight.
3. The dark part of the diurnal cycle considered as a time unit.
4. Darkness.
5. A shortening of nightfall.
6. The period spent sleeping.
7. A period of ignorance or backwardness or gloom.

1. Of, relating to, or associated with the night
2. Intended for use at night
3. Existing, occurring, or functioning at night; active or functioning best at night