Oligopoly has few large firms with interdependent behavior and entry barriers, causing strategic interactions and potential collusion. Characteristics: Few large firms dominating market, Homogeneous or differentiated products, High entry barriers (economies of scale, capital requirements, brand loyalty), Interdependent decision-making (each firm's actions affect others' responses). Pricing strategies: Kinked demand curve model (price-rigid because demand is more elastic above price than below, so firms hesitate to change price), Collusion (implicit or explicit agreement on pricing), Price leadership (dominant firm sets price, others follow), Game theory applications. Game theory: Prisoner's dilemma situation (firms profit more by cooperating but incentive to cheat exists). Concentration measures: Herfindahl index, concentration ratio. Examples: Automobiles (Maruti, Hyundai, Ford), Telecom (Jio, Airtel, Vodafone), Airlines, Cement, FMCG. Regulation: Antitrust, merger controls, anti-collusion laws. ICAI focus: Interdependence, strategic behavior, entry barriers. Exam tip: Oligopoly questions often involve game theory concepts or interdependence in pricing decisions.