How can you Define an Oligopoly?

-Oligopoly is a Market that the Few Dominate (Small Number of Firms have Big Concentration Ratio) -High Barriers to Entry (Supernormal Profits hard to Compete away) -Firms have Differentiated Products (Not the same, but Similar) OR/AND -Firms are Interdependent - Actions of a Firm will effect others -Firms use Competitive or Collusive Strats to make Interdependence work on their Terms