Definition of affair :
1. A material object ( vaguely designated).
2. Action; endeavor.
3. An action or engagement not of sufficient magnitude to be called a battle.
4. Any proceeding or action which it is wished to refer to or characterize vaguely; as, an affair of honor, i. e., a duel; an affair of love, i. e., an intrigue.
5. That which is done or is to be done; matter; concern; as, a difficult affair to manage; business of any kind, commercial, professional, or public; - often in the plural. At the head of affairs. Junius.
dalliance, do, bash, contest, celebration, social occasion, obligation, bout, part, issue, use, occasion, province, passage of arms, combat, routine, matter, mapping, incident, gathering, purpose, mathematical function, involvement, office, mission, operation, gala, duty, responsibility, intrigue, lookout, entanglement, contact, soiree, engagement, relevant, amour, battle, romance, function, fight, thing, affaire, event, rendezvous, work, strife, fete, juncture, encounter, familiarity, festivity, topic, link, subroutine, party, intimacy, group, single-valued function, closeness, map, inter-group communication, love, subprogram, occurrence, subject, sex, participation, case, liaison, role, involution, question, proceeding, skirmish, action, love affair, social function, conflict, entertainment, relationship
business (part of speech: noun)
establishment, commission, consortium, concern, service, market, proprietorship, company, industry, exchange, interest, selling, vocation, situation, posting, employment, labor, commerce, station, partnership, firm, position, busy work, practice, management, job, corporation, barter, business, livelihood, career, activity, trade, calling, transaction, retailing, profession, occupation, holding, negotiation, venture, enterprise, specialty, assignment, merchant
venture (part of speech: noun)