Alarm (noun)

1. A device that makes a loud noise or flashing light as a warning or signal.
2. A feeling of fear or concern about a possible danger or problem.
3. A call to arms.

Origin:

Late middle english: from old french alarme, from italian allarme, from all"arme! "to arms!". the noun sense "warning device" (late 18th century) arose from the verb sense "sound an alarm" (early 17th century).

Examples:

1. He set the alarm for 6:00 am.
2. The alarm went off and woke me up.
3. The alarm on my phone woke me up.
4. The alarm was raised when the fire started.
5. He sounded the alarm of an impending invasion.