Police are agents or agencies, usually of the executive, empowered to enforce the law and to effect public and social order through the legitimatized use of force. The term is most commonly associated with police departments of a state that are authorized to exercise the police power of that state within a defined legal or territorial area of responsibility. The word comes via French from the Latin politia (“civil administration”), which itself derives from the Ancient Greek πόλις, for polis ("city").

The first police force comparable to present-day police was established in 1667 under King Louis XIV in France, although modern police usually trace their origins to the 1800 establishment of the Marine Police in London, the Glasgow Police, and the Napoleonic police of Paris. The first modern police force is also commonly said to be the London Metropolitan Police, established in 1829, which promoted the preventive role of police as a deterrent to urban crime and disorder.

Law enforcement however constitutes only part of policing activity. Policing has included an array of activities in different situations, but the predominant ones are concerned with the preservation of order. In some societies, in the late 18^th century and early 19^th century, these developed within the context of maintaining a layered societal structure and the protection of property.

Alternative names for police force include constabulary, gendarmerie, police department, police service, crime prevention, protective services, law enforcement agency or Garda Síochána, and members can be police officers, troopers, sheriffs, constables, rangers, peace officers or Garda. Russian police and police of the Soviet-era Eastern Europe are (or were) called militsiya.

Ancient China

Law enforcement in Ancient China was carried out by "prefects." The notion of a "prefect" in China has existed for thousands of years. The prefecture system developed in both the Chu and Jin kingdoms of the Spring and Autumn period. In Jin, dozens of prefects were spread across the state, each having limited authority and employment period.

In Ancient China, prefects were government officials appointed by local magistrates, who in turn were appointed by the head of state, usually the emperor of the dynasty. The prefects oversaw the civil administration of their "prefecture," or jurisdiction. Prefects usually reported to the local magistrate, just as modern police report to judges. Under each prefect were "subprefects" who helped collectively with law enforcement of the area. Some prefects were responsible for handling investigations, much like modern police detectives.