What is Police?

Legal Definition
A police force is a constituted body of persons empowered by the state to enforce the law, protect property, and limit civil disorder. Their powers include the legitimized use of force. The term is most commonly associated with police services of a sovereign state that are authorized to exercise the police power of that state within a defined legal or territorial area of responsibility. Police forces are often defined as being separate from military or other organizations involved in the defense of the state against foreign aggressors; however, gendarmerie are military units charged with civil policing.

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 18th and early 19th centuries, these developed within the context of maintaining the class system and the protection of private property. Many police forces suffer from police corruption to a greater or lesser degree. The police force is usually a public sector service, meaning they are paid through taxes.

Alternative names for police force include constabulary, gendarmerie, police department, police service, crime prevention, protective services, law enforcement agency, civil guard or civic guard. Members may be referred to as police officers, troopers, sheriffs, constables, rangers, peace officers or civic/civil guards.

As police are often interacting with individuals, slang terms are numerous. Many slang terms for police officers are decades or centuries old with lost etymology. One of the oldest, "cop," has largely lost its slang connotations and become a common colloquial term used both by the public and police officers to refer to their profession.
-- Wikipedia
Legal Definition
That species of superintendence by magistrates which has principally for its object the maintenance of public tranquillity among the citizens. The officers who are appointed for this purpose are also called the police.

2. The word police has three significations, namely; 1. The first relates to the measures which are adopted to keep order, the, laws and ordinances on cleanliness, health, the markets, &c. 2. The second has for its object to procure to the authorities the means of detecting even the smallest attempts to commit crime, in order that the guilty may be arrested before their plans are carried into execution, and delivered over to the justice of the country. 3. The third comprehends the laws, ordinances and other measures which require the citizens to exercise their rights in a particular form.

3. Police has also been divided into administrative police, which has for its object to maintain constantly public order in every part of the general administration; and into judiciary police, which is intended principally to prevent crimes by punishing the criminals. Its object is to punish crimes which the administrative police has not been able to prevent.
-- Bouviers Law Dictionary
Legal Definition
Police is the function of that branch of the administrative machinery of government which is charged with the preservation of public order and tranquillity, the promotion of the public health, safety, and morals, and the prevention, detection, and punishment of crimes. See State v. Hine, 59 Conn. 50, 21 Atl. 1024, 10 In R. A. 83; Monet v. Jones, 10 Smedes & M. (Miss.) 247; People v. Squire, 107 N. Y. 593, 14 N. E. 820, 1 Am. St. Rep. 893; Logan v. State, 5 Tex. App. 314. The police of a state, in a comprehensive sense, embraces its whole system of internal regulation, by which the state seeks not only to preserve the public order and to prevent offenses against the state, but also to establish for the intercourse of citizen with citizen those rules of good manners and good neighborhood which are calculated to prevent a conflict of rights, and to insure to each the uninterrupted enjoyment of his own, so far as is reasonably consistent with a like enjoyment of rights by ethers. Cooley, Const. Lim. 572. It is defined by Jeremy Bentham in his works; "Police is in general a system of precaution, either for the prevention of crime or of calamities. Its business may be distributed into eight distinct branches:

(1) Police for the prevention of offenses ;

(2) police for the prevention of calamities;

(3) police for the prevention of epidemic diseases;

(4) police of chariur;

(5) police of interior communications;

(6) police of public amusements;

(7) police for recent intelligence;

(8) police for registration." Canal Com'rs v. Willamette Transp. Co., 6 Or. 222.
See also
-- Black's Law Dictionary
Legal Definition
-- Ballentine's Law Dictionary