An oligopoly is a market form in which a market or inustry is dominated by a small number of sellers (oligopolists). The word is derived from the Greek for a few over many. Because there are few participants in this type of market, each oligopolist is aware of the actions of the others. The decisions of one firm influence, and are influenced by the decisions of other firms. Strategic planning by oligopolists always involves taking into account the likely responses of the other market participants. This causes oligopolistic markets and industries to be at the highest risk for collusion.