Emergency (noun)

1. A serious, unexpected, and often dangerous situation requiring immediate action.
2. A state of urgency requiring immediate action.
3. A state of emergency, crisis, or danger.
4. A sudden or unexpected event that requires immediate action.
5. A condition requiring immediate action to avoid a serious outcome.

Origin:

Early 17th century: from latin emergency, from e- (variant of ex-) "out" + mergere "to dip, submerge" in the sense "arise unexpectedly".

Examples:

1. The emergency services arrived quickly.
2. The hospital has a plan for emergency situations.
3. He called for emergency assistance.
4. The emergency broadcast system was activated.
5. She called the emergency number when her house caught on fire.