In economics, a market dominated by a single seller is called a monopoly.
A monopoly exists when one person or company is the only supplier of a particular good or service, with no close substitutes and significant barriers preventing competitors from entering. Because the seller faces little direct competition, it may have enough market power to influence prices or restrict output. A monopolist is therefore often described as a price maker, although demand still limits what it can charge.
Monopolies can arise naturally when one network or infrastructure system is most efficient, such as some water or electricity services. They can also be created by government grants, patents, exclusive licenses, control of a scarce resource, or the collapse of competitors. Competition laws in many countries regulate conduct that abuses monopoly power.
A monopoly should not be confused with a monopsony, which has one buyer, or an oligopoly, in which a small number of sellers dominate. A duopoly is a special type of oligopoly with two major sellers.