Round-robin tournament

A round-robin tournament (or all-play-all tournament) is a competition "in which each contestant meets all other contestants in turn".Webster's Third New International Dictionary of the English Language, Unabridged (1971, G. & C. Merriam Co), p.1980.

Terminology

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 III and All America Football Conference for exceptions).

A round-robin tournament with four players is sometimes called a "quad". In croquet and tennis clubs in the United Kingdom, a round-robin tournament is often called an American 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.

Use

In sports with a large number of competitive matches per 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...
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