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.
Demonstrations can be used to show a viewpoint (either positive or negative) regarding a public issue, especially relating to a perceived grievance or social injustice. A demonstration is usually considered more successful if more people participate.
Historian Eric Hobsbawm wrote of demonstrations:
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… like sex 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.