Definition of "convention"

convention

/kənˈvɛn.ʃən/

noun
countable and uncountable, plural conventions
1. A meeting or gathering.
  Quotations
  The CEF and the legal advocacy groups that have been responsible for its tremendous success over the past ten years are determined to "Knock down all doors, all the barriers, to all 65,000 public elementary schools in America and take the Gospel to this open mission field now! Not later, now!" in the words of a keynote speaker at the CEF's national convention in 2010.
  2012 May 30, Katherine Stewart, “How Christian fundamentalists plan to teach genocide to schoolchildren”, in the Guardian‎
2. A formal deliberative assembly of mandated delegates.
3. The convening of a formal meeting.
4. A formal agreement, contract, rule, or pact.
5. (international law) A treaty or supplement to such.
6. A practice or procedure widely observed in a group, especially to facilitate social interaction; a custom.
  Quotations
  In order to account for this, we might propose to make the Prepositional Phrase an optional constituent of the Verb Phrase: this we could do by re- placing rule (28) (ii) by rule (40) below:(40) VP → V AP (PP)(Note that a constituent in parentheses is, by convention, taken to be optional.)
  1988, Andrew Radford, Transformational grammar: a first course, Cambridge, UK: Cambridge University Press, page 127