Monopoly has one firm producing unique product with barriers preventing entry, giving pricing power and potential excess profit. Characteristics: Single seller, unique product with no close substitutes, High entry barriers (patent, economies of scale, resource control, legal restrictions), Price-maker (sets price where demand and cost permit). Barriers to entry: Natural monopoly (declining AC over entire range), Patents and intellectual property, Control of essential resources, Government licensing, Brand loyalty, Economies of scale. Profit maximization: Produces where MR = MC; sets price from demand curve at that output level; Price > MC in equilibrium; economic profit possible even in long run. Demand curve: Firm's demand = market demand (downward sloping); monopolist must lower price to sell more (Price > MR). Efficiency: Not allocatively efficient (P > MC means deadweight loss); may not be productively efficient. Examples: Railways (historically), telecommunications (historical), patent medicines, local utilities. Regulation: Price controls, forced competition, quality standards. ICAI focus: Entry barriers, pricing power, efficiency loss. Exam tip: "Monopolist produces less at higher price than competitive firm would" is the standard comparison.