A convention is a gathering of individuals who meet at a pre-arranged place and time in order to discuss or engage in some common interest. The most common conventions are based upon fandom, industry, and profession. Fan conventions usually feature sales, people dressed up as their favorite characters, and guest celebrities. Trade conventions typically focus on a particular industry or industry segment, and feature keynote speakers, vendor displays, and other information and activities of interest to the event organizers and attendees. Professional conventions focus on issues of concern to the profession and advancements in the profession. Such conventions are generally organized by societies dedicated to promotion of the topic of interest.
A convention is a rule or a selection from among two or more alternatives, where the rule or alternative is agreed upon among participants. For instance, the convention in America and Germany is that motorists drive on the right side of the road, whereas in England and Barbados they drive on the left. The extent to which justice is conventional (as opposed to natural or objective) is historically an important debate among philosophers.
In governments, convention is a set of unwritten rules which the participants in the government are expected to follow. These rules can be ignored only if justification is clear, or can be provided. Otherwise, consequences are sure to follow. Consequences may include ignoring some other convention that has until now been followed. Convention is particularly important in the United Kingdom and former British colonies such as Canada and Australia where many of the rules of government are unwritten. An example of conventions being broken is the Australian Constitutional Crisis of 1975.
The National Convention or Convention, in France, comprised the constitutional and legislative assembly which sat from September 20, 1792 to October 26, 1795.
In any form of art there are conventions that may simply be expectations (for example, that paintings are rectangular) or stock devices (a comedy ends with a marriage, but a cowboy film can end with the hero riding off into the sunset). There are generic conventions that are tied very closely to a particular genre - and may even help to define what it is.