bedtime
Synonym discussion
Sense: noun/1
Bedtime is the usual hour for going to sleep, especially in daily family routines. Lights-out is narrower and more literal: it is the moment when a school, camp, or army group expects everyone to turn off the lights and settle down. Sleep time is a simple phrase adults often use with very young children, and it sounds less fixed and less dictionary-like than bedtime. Curfew is different again because it is the time you must be home, not the time you must be asleep. A teenager may have a ten o'clock curfew but an eleven o'clock bedtime. Parents often say 'It's bedtime' at home, while a camp leader may announce 'lights-out in five minutes.'
Common collocations
Etymology
A plain English compound joining bed and time. It became the ordinary name for the hour when a person should go to bed, especially in family routines. Both parts are very old in English: bed comes from Old English, and time does too, so bedtime is built from native English words rather than from a later borrowing.