Police

A person or group from or with the job of protecting civilians. Popular ones include: LAPD, NYPD.

Police protects the Law also known as "Policy" most likely the origin of said word.

Other synonyms include
Law Enforcement
Officer
Police Officer
Law Enforcer
Sheriff

The police is on their way to that building to catch the fugitives.

This is the police! Open up!

Police Departments are important to city safety!