What term describes the control of a market by a single business entity?

The term that describes the control of a market by a single business entity is "monopoly." In a monopoly, one company or organization dominates the entire market for a particular product or service, effectively becoming the sole provider. This situation typically limits competition, allowing the monopolizing firm to set prices, control supply, and influence market conditions without the need to respond to rivals.

In contrast, an oligopoly involves a few businesses that control a significant portion of the market, leading to interdependent pricing and decision-making among those firms. A duopoly is a specific type of oligopoly where only two companies dominate the market. A cartel is a formal agreement among competing firms to control prices or limit production to maximize profits, which is more about collusion rather than a single entity controlling the market. Therefore, "monopoly" is the accurate term for a single business entity's control over a market.