Oligopoly

An oligopoly is a market controlled by a small number of large companies, rather than one monopoly or many small competitors. Prices, capacity, and competitive behavior all depend heavily on what the other few players do, since each company's actions directly affect the others' market share.

Oligopolies often form in industries with very high costs to enter, building a competitive factory, network, or platform can require billions of dollars and years of specialized expertise, so new competitors rarely show up. That scarcity of players is itself a kind of moat: the existing companies don't need to worry about a steady stream of new entrants undercutting them, even if they still compete hard against each other.