association

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The act of associating or the state of being associated.
• noun An organized body of people who have an interest, activity, or purpose in common; a society.
• noun A mental connection or relation between thoughts, feelings, ideas, or sensations.
• noun A remembered or imagined feeling, emotion, idea, or sensation linked to a person, object, or idea.
• noun A correlation or causal connection.
• noun Chemistry Any of various processes of combination, such as hydration, solvation, or complex-ion formation, depending on relatively weak chemical bonding.
• noun Ecology A large number of organisms in a specific geographic area constituting a community with one or two dominant species.

from The Century Dictionary.

• noun The act of associating or the state of being associated. Connection of persons or things; union.
• noun A union or connection of ideas. See association of ideas, below.
• noun An organized union of persons for a common purpose; a body of persons acting together for the promotion of some object of mutual interest or advantage; a partnership, corporation, or society: as, the Association for the Advancement of Science; a political or charitable association.
• noun In physical chemistry, the union of chemical molecules to form more complex aggregates; especially, the union of the molecules of a vapor to form more complex aggregates when the temperature is reduced nearly to the boiling-point, or when they condense into liquids.
• noun In phytogeography, the aggregation of plant individuals initiated by reproduction on the spot of growth, but finally determined by environment. See formation and plant association.
• noun A local aggregation of plants within a formation characterized more by the species which compose it than by any biological peculiarity.

from the GNU version of the Collaborative International Dictionary of English.

• noun The act of associating, or state of being associated; union; connection, whether of persons of things.
• noun Mental connection, or that which is mentally linked or associated with a thing.
• noun Union of persons in a company or society for some particular purpose. Specifically, as among the Congregationalists, a society, consisting of a number of ministers, generally the pastors of neighboring churches, united for promoting the interests of religion and the harmony of the churches.
• noun (Physiol.) the combination or connection of states of mind or their objects with one another, as the result of which one is said to be revived or represented by means of the other. The relations according to which they are thus connected or revived are called the law of association. Prominent among them are reckoned the relations of time and place, and of cause and effect.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The act of associating.
• noun The state of being associated; a connection to or an affiliation with something.
• noun A group of persons associated for a common purpose; an organization; society.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a formal organization of people or groups of people
• noun a social or business relationship
• noun (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
• noun the act of consorting with or joining with others
• noun the state of being connected together as in memory or imagination
• noun (chemistry) any process of combination (especially in solution) that depends on relatively weak chemical bonding
• noun the process of bringing ideas or events together in memory or imagination
• noun a relation resulting from interaction or dependence