Policeman (noun)

1. A man who is a member of a police force.
2. A man whose job is to enforce laws and maintain order in the community.
3. A man who works in a police department.

Origin:

Late 18th century: from police + man. the word originally denoted a man whose duty was to keep order in public places.

Examples:

1. He was a policeman for 20 years.
2. The policeman gave him a ticket.
3. She spoke to the policeman at the station.
4. He saw a group of policemen on the corner.
5. The little boy wanted to be a policeman when he grew up.