Other forms: police officers
A police officer is a person whose job involves enforcing the law. On a given day, a police officer might issue a ticket to a speeding driver, respond to a noise complaint about a barking dog, or direct traffic during a parade.
Police officers are members of a police force, tasked with upholding laws, investigating crimes, and arresting criminals, among many other duties. Most police officers attend an academy and take a written exam before they can join a force. You can also use the terms policeman and policewoman, but those sound a bit old-fashioned — and police officer includes everyone on the police force.