Police forces are government organisations charged with the responsibility of maintaining law and order. The word comes from the French, and less directly from the Greek politeia, referring to government or administration. The word police was coined in France in the 18th century. The police may also be known as a constabulary, after constables, who were the first police officers.

n most Western legal systems, the major role of the police is to discourage and investigate crimes, and if able to apprehend suspected perpetrator(s), to detain them, and inform the appropriate authorities. See criminal law.

Police are often used as an emergency service and may provide a public safety function at large gatherings, as well as in emergencies, disasters, and search and rescue situations. To provide a prompt response in emergencies, the police often co-ordinate their operations with fire and medical services. In many countries there is a common emergency service number that allows the police, firefighters or medical services to be summoned to an emergency.

Police are also responsible for reporting minor offenses by issuing citations which typically may result in the imposition of fines, particularly for violations of traffic law. Police sometimes involve themselves in the maintenance of public order, even where no legal transgressions have occurred -- for example, in some Australian jurisdictions, people who are drunk and causing a public nuisance may be removed to a "drying-out centre" until they recover from the effects of the alcohol.

In many countries, particularly those with a federal system of government, there may be several police or police-like organisations, each serving different levels of government and enforcing different subsets of the applicable law. In the United States of America, for instance, there are typically police forces (city police, county sheriff, state trooper etc.) run by local and state authorities, as well as several federal law enforcement agencies (including the Federal Bureau of Investigation, the Bureau of Alcohol, Tobacco and Firearms, the United States Marshals Service, the Drug Enforcement Administration and the Secret Service), endowed with police or quasi-police roles.

In countries following the French model, there may be two separate national police agencies: the National Police and the Gendarmerie, with overlapping but different jurisdiction, possibly in addition to local police forces.

Most countries are members of the International Criminal Police Organization - Interpol, established to detect and fight trans-national crime and provide for international co-operation and co-ordination of other police activities, such as notifying relatives of the death of foreign nationals. Interpol does not conduct enquiries nor arrests by itself, but only serves as a central point for information on crime, suspects and criminals. Political crimes are excluded from its competencies.