n.

1. a formal organization of people or groups of people
   
   • he joined the Modern Language Association
2. the act of consorting with or joining with others
   
   • you cannot be convicted of criminal guilt by association
3. the state of being connected together as in memory or imagination
   
   • his association of his father with being beaten was too strong to break
4. a social or business relationship;
   affiliation, tie, tie-up
   
   • a valuable financial affiliation
   • he was sorry he had to sever his ties with other members of the team
   • many close associations with England
5. the process of bringing ideas or events together in memory or imagination;
   connection, connexion
   
   • conditioning is a form of learning by association
6. a relation resulting from interaction or dependence
   
   • flints were found in association with the prehistoric remains of the bear
   • the host is not always injured by association with a parasite
7. (chemistry) any process of combination (especially in solution) that depends on relatively weak chemical bonding
8. (ecology) a group of organisms (plants and animals) that live together in a certain geographical region and constitute a community with a few dominant species