A demonstration or street protest is action by a mass group or collection of groups of people in favor of a political or other cause; it normally consists of walking in a mass march formation and either beginning with or meeting at a designated endpoint, or rally, to hear speakers. Historian Eric Hobsbawm says, "Next to sex, the activity combining bodily experience and intense emotion to the highest degree is the participation in a mass demonstration at a time of great public exaltation. Unlike sex, which is essentially individual, it is by its nature collective...and it can be prolonged for hours....It implies some physical action--marching, chanting slogans, singing — through which the merger of the individual in the mass, which is the essence of the collective experience, finds expression.'
Actions such as blockades and sit-ins may also be referred to as demonstrations. Demonstrations can be nonviolent or violent (usually referred to by participants as "militant"), or can begin as nonviolent and turn violent dependent on circumstances. Sometimes riot police or other forms of law enforcement become involved. In some cases this may be in order to try to prevent the protest from taking place at all. In other cases it may be to prevent clashes between rival groups, or to prevent a demonstration from spreading and turning into a riot.
The term has been in use since the mid-19th century, as was the term 'monster meeting', which was coined initially with reference to the huge assemblies of protesters inspired by Daniel O'Connell in Ireland. Demonstrations are a form of activism, usually taking the form of a public gathering of people in a rally or walking in a march. Thus, the opinion is demonstrated to be significant by gathering in a crowd associated with that opinion.
The police are 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 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. Some parts of the world may suffer from police corruption.
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. Police of the Soviet-era Eastern Europe were (or are, in some cases, as in Belarus) called the militsiya. The Irish police are called the Garda Síochána ("guardians of the peace"); a police officer is called a garda. As police are often in conflict with individuals, slang terms are numerous. Many slang terms for police officers are decades or centuries old with lost etymology.