noun

• (uncountable) The act of associating.
  "And it is a characteristic of man that he alone has any sense of good and evil, of just and unjust, and the like, and the association of living beings who have this sense makes a family and a state."
• (countable) The state of being associated; a connection to or an affiliation with something.
  ""Well," exclaimed Lady Marchmont, breathing the perfume with which a honeysuckle, wound around an old ash, filled the air, "I do confess that I like common flowers better than any. The hothouse plant has no associations.""
• (statistics) Any relationship between two measured quantities that renders them statistically dependent (but not necessarily causal or a correlation).
• (object-oriented programming) Relationship between classes of objects that allows one object instance to cause another to perform an action on its behalf.