In economics, a monopoly is a market structure in which one seller controls the supply of a product or service.
A monopolist has substantial market power because customers cannot easily switch to an alternative supplier. Barriers to entry can include legal restrictions, control of an essential resource, very large fixed costs, network effects, or a natural cost advantage. A monopoly may therefore be able to influence price, output, or both.
The word combines the Greek roots monos, meaning “single,” and pōlein, meaning “to sell.” Economists often compare monopoly with perfect competition, where many sellers offer similar products and no single firm controls the market price.
A monopoly is not the same as a monopsony. A monopsony has one dominant buyer rather than one dominant seller. An oligopoly, by contrast, has a small number of significant sellers. Governments may regulate monopolies, break up anticompetitive arrangements, or permit some natural monopolies under oversight.