Oligopoly A monopoly is an industry consisting a single firm a duopoly is an industry consisting of two firms An oligopoly is an industry consisting of a few firms. Particularly, each firm's own price or output decisions affect its competitors'profitsOligopoly A monopoly is an industry consisting a single firm. A duopoly is an industry consisting of two firms. An oligopoly is an industry consisting of a few firms. Particularly, each firm’s own price or output decisions affect its competitors’ profits