A monopoly must be distinguished from monopsony, in which there is only one buyer of a product or service ; a monopoly may also have monopsony control of a sector of a market. Likewise, a monopoly should be distinguished from a cartel (a form of oligopoly), in which several providers act together to coordinate services, prices or sale of goods. Monopolies, monopsonies and oligopolies are all situations where one or a few of the entities have market power and therefore must interact with their customers (monopoly), suppliers (monopsony) and the other firms (oligopoly) in a game theoretic manner – meaning that expectations about their behavior affects other players’ choice of strategy and vice versa. This is to be contrasted with the model of perfect competition where firms are price takers and do not have market power. Monopolists typically produce fewer goods and sell them at a higher price than under perfect competition, resulting in abnormal and sustained profit. (See also Bertrand, Cournot or Steckelberg equilibria, market power, market share, market concentration, Monopoly profit, industrial economics).

Monopolies can form naturally or through vertical or horizontal mergers. A monopoly is said to be coercive when the monopoly firm actively prohibits competitors from entering the field or punishes competitors who do (see Chainstore paradox).

In many jurisdictions, competition laws place specific restrictions on monopolies. Holding a dominant position or a monopoly in the market is not illegal in itself, however certain categories of behavior can, when a business is dominant, be considered abusive and therefore be met with legal sanctions. A government-granted monopoly or legal monopoly, by contrast, is sanctioned by the state, often to provide an incentive to invest in a risky venture or enrich a domestic interest group. Patents, copyright, and trademarks are all examples of government granted and enforced monopolies. The government may also reserve the venture for itself, thus forming a government monopoly.

Market structures

In economics, monopoly is a pivotal area to the study of market structures, which directly concerns normative aspects of economic competition, and sets the foundations for fields such as industrial organization and economics of regulation. There are four basic types of market structures under traditional economic analysis: perfect competition, monopolistic competition, oligopoly and monopoly. A monopoly is a market structure in which a single supplier produces and sells the product. If there is a single seller in a certain industry and there are no close substitutes for the goods being produced, then the market structure is that of a “pure monopoly”. Sometimes, there are many sellers in an industry and/or there exist many close substitutes for the goods being produced, but nevertheless firms retain some market power. This is called monopolistic competition, whereas in oligopoly the main theoretical framework revolves around firm’s strategic interactions.

In general, the main results from this theory compare price-fixing methods across market structures, analyse the impact of a certain structure on welfare, and play with different variations of technological/demand assumptions in order to assess its consequences on the abstract model of society. Most economic textbooks follow the practice of carefully explaining the perfect competition model, only because of its usefulness to understand “departures” from it (the so called imperfect competition models).

The boundaries of what constitutes a market and what doesn’t is a relevant distinction to make in economic analysis. In a general equilibrium context, a good is a specific concept entangling geographical and time-related characteristics (grapes sold in October 2009 in Moscow is a different good from grapes sold in October 2009 in New York). Most studies of market structure relax a little their definition of a good, allowing for more flexibility at the identification of substitute-goods. Therefore, one can find an economic analysis of the market of grapes in Russia, for example, which is not a market in the strict sense of general equilibrium theory.