noun

• (often in the plural) Something which is done or is to be done; business of any kind, commercial, professional, or public.
• Any proceeding or action which it is wished to refer to or characterize vaguely.
• (military) An action or engagement not of sufficient magnitude to be called a battle.
• A material object (vaguely designated).
• An adulterous relationship (from affaire de cœur, affair of the heart).
• An otherwise illicit romantic relationship, such as with someone who is not one's regular partner (boyfriend, girlfriend).
• A person with whom someone has an adulterous relationship.
• A party or social gathering, especially of a formal nature.
• (slang, now rare) The (male or female) genitals.