1) The regular coming together of large groups of individuals, generally to discuss a particular subject. A congress will often last several days and have several simultaneous sessions. The length of time between congresses is usually established in advance of the implementation stage, and can be either pluri-annual or annual. Most international or world congresses are of the former type while national congresses are more frequently held annually. 2) Meeting of an association of delegates or representatives from constituent organizations. 3) European term for convention.