alarm

To warn someone of danger or an impending problem.

"The system is designed to alarm users of critical errors."

A warning sound or device, such as a bell or siren.

"The fire alarm blared loudly throughout the building."

A sudden feeling of fear or anxiety, often about danger.

"The news caused widespread alarm among residents."

To cause someone to feel sudden fear or anxiety.

"The sudden noise alarmed the sleeping child."

A clock or device set to wake someone at a specific time.

"My alarm goes off at seven every morning."