1. 1. The period between sunset and sunrise, especially the hours of darkness.
   2. This period considered as a unit of time: for two nights running.
   3. This period considered from its conditions: a rainy night.
2. The period between dusk and midnight of a given day: either late Thursday night or early Friday morning.
3. 1. The period between evening and bedtime.
   2. This period considered from its activities: a night at the opera.
   3. This period set aside for a specific purpose: Parents' Night at school.
4. 1. The period between bedtime and morning: spent the night at a motel.
   2. One's sleep during this period: had a restless night.
5. Nightfall: worked from morning to night.
6. Darkness: vanished into the night.
7. 1. A time or condition of gloom, obscurity, ignorance, or despair: "In a real dark night of the soul it is always three o'clock in the morning" (F. Scott Fitzgerald).
   2. A time or condition marked by absence of moral or ethical values: "He never would have let us go untroubled into the night of private greed" (Anthony Lewis).

1. Of or relating to the night: the night air.
2. Intended for use at night: a night light.
3. Working during the night: the night nurse.
4. Active chiefly at night: night prowlers.
5. Occurring after dark: night baseball.

[Middle English, from Old English niht.]

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.