accord, accordance, agreement, alliance, coaction, coadjument, coadjuvancy, coagency, coalition, coefficiency, collaboration, combination, combined action, combined effort, compatibility, complicity, concord, concordance, concurrence, concurrency, confederation, conjunction, consentaneity, consonance, cooperation, fusion of interests, harmony, joint action, joint operation, merger, mutual assistance, pool, rapport, synergy, teamwork, unanimity, unison, unity
associated concepts: acting in concert
affiliation (connectedness), cartel, coherence, collusion, combine (act in concert), conciliation, concordance, conformity (agreement), conjunction, connivance, connive, consensus, consolidate (unite), conspiracy, conspire, contribution (participation), cooperate, federate, federation, orchestrate, propinquity (similarity), synergy, union (unity)
Burton's Legal Thesaurus. William C. Burton. 2006
See art and part.
Collins dictionary of law. W. J. Stewart. 2001.