convention vs symposium

convention

noun
  • The convening of a formal meeting. 

  • A formal agreement, contract, rule, or pact. 

  • A treaty or supplement to such. 

  • A meeting or gathering. 

  • A practice or procedure widely observed in a group, especially to facilitate social interaction; a custom. 

  • A formal deliberative assembly of mandated delegates. 

symposium

noun
  • A conference or other meeting for discussion of a topic, especially one in which the participants make presentations. 

  • A drinking party in Ancient Greece, especially one with intellectual discussion. 

  • A collection of essays, articles or papers on a particular subject by a number of contributors. 

How often have the words convention and symposium occurred in a corpus of books? (source: Google Ngram Viewer )