noun (n)

• the act of sharing in the activities of a group(noun.act)

  Synonym:
  engagement, involution, participation
  Antonym:
  non-engagement, non-involvement, nonparticipation
  

  source: wordnet30
• a connection of inclusion or containment(noun.linkdef)

  Example:
  He escaped involvement in the accident.
  There was additional involvement of the liver and spleen.
  

  source: wordnet30
• a sense of concern with and curiosity about someone or something(noun.cognition)

  Synonym:
  interest
  

  source: wordnet30
• a usually secretive or illicit sexual relationship(noun.state)

  Synonym:
  affair, affaire, amour, intimacy, liaison
  

  source: wordnet30
• the condition of sharing in common with others (as fellows or partners etc.)(noun.state)

  Synonym:
  participation
  

  source: wordnet30
• The act of involving, or the state of being involved.(noun)

  source: webster1913