0 the part of every 24-hour period when it is dark because there is very little light from the sun: --
1 the period of time between the late afternoon and going to bed; the evening: --
2 a friendly way of saying goodbye when you leave someone in the evening or before going to bed or to sleep: --
Night, sweetheart! Sleep well!
3 the part of every 24-hour period when it is dark because there is no direct light from the sun: --
They did a charity performance on the first night, to raise money for AIDS research.
I've been out every night this week.
It was lovely to see your mum and dad at the school concert last night.
Get a good night's sleep and you'll feel better able to cope.