Curfew is a rule or law that sets a time that certain people have to be off the streets. A town may set a curfew for teenagers, for example, although many parents impose a stricter curfew for their own kids.
Historically, a curfew was signaled by the ringing of a bell meant to alert residents that it was time to put out their hearth fires. The word curfew comes from an Old French word cuevrefeu, "cover fire," cuevre meaning to cover, and feu meaning fire. Over time, curfew has come to refer to getting people off the streets at night and into their homes, often during times of civil unrest.