noun

1. the act of associating
2. the state of being associated; companionship; fellowship; partnership
3. an organization of persons having common interests, purposes, etc.; society; league
4. a connection in the mind between ideas, sensations, memories, etc.
5. the use of such connections as a literary device or psychoanalytic technique
6. a group of organisms living together in the same environment and forming a large, distinct component of a biome an oak forest association within a deciduous forest biome
7. Chem. the joining by relatively weak chemical bonds of two or more molecules of the same or different substances into a larger aggregate, as in polymerization

Etymology: ML associatio, a joining with: see associate