Oligopoly:

When a few FIRMS dominate a market. Often they can together behave as if they were a single MONOPOLY, perhaps by forming a CARTEL. Or they may collude informally, by preferring gentle NON-PRICE COMPETITION to a bloody PRICE war. Because what one firm can do depends on what the other firms do, the behaviour of oligopolists is hard to predict. When they do compete on price, they may produce as much and charge as little as if they were in a market with PERFECT COMPETITION.