[custom_adv] A demonstration is action by a mass group or collection of groups of people in favor of a political or other cause or people partaking in a protest against a cause of concern; it often consists of walking in a mass march formation and either beginning with or meeting at a designated endpoint, or rally, to hear speakers. It is different from mass meeting. [custom_adv] Actions such as blockades and sit-ins may also be referred to as demonstrations. [custom_adv] Demonstrations can be nonviolent or violent (usually referred to by participants as "militant"), or can begin as nonviolent and turn violent depending on the circumstances. [custom_adv] 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. [custom_adv] In other cases, it may be to prevent clashes between rival groups, or to prevent a demonstration from spreading and turning into a riot. [custom_adv] 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 (1775–1847) in Ireland. [custom_adv] Demonstrations are a form of activism, usually taking the form of a public gathering of people in a rally or walking in a march. [custom_adv] Thus, the opinion is demonstrated to be significant by gathering in a crowd associated with that opinion. [custom_adv] Thus, the opinion is demonstrated to be significant by gathering in a crowd associated with that opinion.