In sport, a bye is the preferential status of a player or team that is automatically advanced to the next round of a tournament, without having to play an opponent in an early round.
In knockout (elimination) tournaments they can be granted either to reward the highest ranked participant(s) or assigned randomly, to make a working bracket if the number of participants is not a power of two (e.g. 16 or 32).
In round-robin tournaments, usually one competitor gets a bye in each round when there are an odd number of competitors, as it is impossible for all competitors to play in the same round. However, over the whole tournament, each plays the same number of games as well as sitting out for the same number of rounds. The "Berger Tables" used by FIDE for chess tournaments, provide pairings for even numbered pools and simply state that "Where there is an odd number of players, the highest number counts as a bye."
Similar to the round-robin context, in league sports with weekly regular-season play such as gridiron football or rugby, a team not scheduled to play on a given week or fixture (competition period) can be said to be on its "bye week". Byes are necessary if there is an odd number of teams, but may be used even with an even number of teams, such as to provide rest breaks as has been done in the National Football League (NFL).