Noun

(economics) A market situation in which two companies exclusively provide a particular product or service.

* {{quote-news

, year=2012 , date=June 29 , author=Kevin Mitchell , title=Roger Federer back from Wimbledon 2012 brink to beat Julien Benneteau , work=the Guardian citation , page= , passage=In 2011, his spirit and body were shattered by Jo-Wilfried Tsonga in the semi-finals. Last night, the stakes were just as high – even though the tournament is not out of the first week – because there is a creeping perception that the Federer-Nadal duopoly is slowly giving way under pressure from below. }}