Which term best describes a market structure of limited competition in which the market is shared by a small number of sellers?

A monopoly exists when a single seller controls the entire market for a good or service, eliminating competition entirely. This structure differs fundamentally from an oligopoly, where multiple firms coexist and compete with one another, albeit in a limited capacity.

Monopolistic competition describes a market structure where many firms sell products that are similar but not identical, allowing for some price-setting power. While there is competition, the number of sellers is greater than in an oligopoly, making this choice inaccurate for the definition provided in the question.

Perfect competition is characterized by a large number of buyers and sellers, all of whom sell identical products. In this scenario, no single seller can influence market prices, which is the opposite of an oligopoly where a few sellers have considerable market power and influence.