duopoly

noun3

1. •
   An economic condition in which two sellers exert most control over the market of a commodity.

   • Modern examples of duopoly include the American markets for credit cards (Visa and MasterCard), smartphones (Apple and Google), soft drinks (Coca-Cola and Pepsi), and airplanes (Airbus and Boeing).
2. •
   The domination of a field of endeavour by two entities or people.

   • First past the post voting has long maintained American politics as an effective duopoly where power simply alternates between two main parties.
3. •
   A situation in which two or more radio or television stations in the same city or community share common ownership.