Double round robin

A round-robin tournament (or all-play-all tournament) is a competition "in which each contestant meets all other contestants in turn". It contrasts with an elimination tournament.

The term round-robin is derived from the French term ruban, meaning "ribbon". Over a long period of time, the term was corrupted and idiomized to robin.

In a single round-robin schedule, each participant plays every other participant once. If each participant plays all others twice, this is frequently called a double round-robin. The term is rarely used when all participants play one another more than twice, and is never used when one participant plays others an unequal number of times (as is the case in almost all of the major United States professional sports leagues – see AFL (1940–41) and All-America Football Conference for exceptions).

In the United Kingdom, a round-robin tournament is often called an American tournament in sports such as tennis or billiards which usually have knockout tournaments. In Italian it is called girone all'italiana (literally "Italian-style circuit"). In Serbian it is called the Berger system (Бергеров систем, Bergerov sistem), after chess player Johann Berger. A round-robin tournament with four players is sometimes called "quad" or "foursome".

In sports with a large number of competitive matches for season, double round-robins are common. Most association football leagues in the world are organized on a double round-robin basis, in which every team plays all others in its league once at home and once away. This system is also used during qualification for major tournaments such as the FIFA World Cup and the respective continental tournaments (e.g. UEFA European Championship, CONCACAF Gold Cup, etc.). There are also round-robin chess, draughts, go, curling and Scrabble tournaments. The World Chess Championship decided in 2005 and in 2007 on an eight-player double round-robin tournament where each player faces every other player once as white and once as black.

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