Every citizen has the right to vote.

I use a citizens band radio to communicate with other drivers on the road.

The senior citizen enjoys taking walks in the park.

A citizen arrest is the act of apprehending a person by a private individual rather than a law enforcement officer.

A citizen's arrest is the apprehension of a person by a private citizen, rather than by a law enforcement officer or agent of the state, who has witnessed a crime or has reasonable suspicion that a person has committed a crime.

She obtained citizenship after living in the country for five years.