1a way in which something is usually done:to attract the best patrons the movie houses had to ape the conventions and the standards of theatres
[mass noun] behaviour that is considered acceptable or polite to most members of a society:he was an upholder of convention and correct form [count noun]:the law is felt to express social conventions
2an agreement between states covering particular matters, especially one less formal than a treaty:the convention, signed by the six states bordering on the Black Sea, aims to prevent further pollution
3a large meeting or conference, especially of members of a political party or a particular profession or group:the party held its biennial convention
North American an assembly of the delegates of a political party to select candidates for office.
a body set up by agreement to deal with a particular issue:the convention is a UN body responsible for the regulation of sea dumping
historical a meeting of Parliament without a summons from the sovereign.
4 Bridge a bid or system of bidding by which the bidder tries to convey specific information about the hand to their partner, as opposed to seeking to win the auction.
late Middle English(in sense 3): via Old French from Latin conventio(n-) 'meeting, covenant', from the verb convenire(see convene). sense 1 dates from the late 18th century
convention in other Oxford dictionaries
Definition of convention in the US English dictionary