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A tournament is a competition involving a relatively large number of competitors, all participating in a sport or game. More specifically, the term may be used in either of two overlapping senses: # One or more competitions held at a single venue and concentrated into a relatively short time interval. # A competition involving multiple matches, each involving a subset of the competitors, with the overall tournament winner determined based on the combined results of these individual matches. These are common in those sports and games where each match must involve a small number of competitors: often precisely two, as in most team sports, racket sports and combat sports, many card games and board games, and many forms of competitive debating. Such tournaments allow large numbers to compete against each other in spite of the restriction on numbers in a single match. These two senses are distinct. All golf tournaments meet the first definition, but while match play tournaments meet the second, stroke play tournaments do not, since there are no distinct matches within the tournament. In contrast, football (soccer) leagues like the Premier League are tournaments in the second sense, but not the first, having matches spread across many stadia over a period of up to a year. Many tournaments meet both definitions; for example, the Wimbledon tennis championship. A tournament-match (or ''tie'' or ''fixture'' or ''heat'') may involve multiple game-matches (or ''rubbers'' or ''legs'') between the competitors. For example, in the Davis Cup tennis tournament, a tie between two nations involves five rubbers between the nations' players. The team that wins the most rubbers wins the tie. In the later rounds of UEFA Champions League of football (soccer), each fixture is played over two legs. The scores of each leg are added, and the team with the higher aggregate score wins the fixture, with away goals used as a tiebreaker and a penalty shootout if away goals cannot determine a winner. ==Knockout tournaments== (詳細はKnockout tournament elimination tournament redirect here--> A knockout tournament or elimination tournament is divided into successive rounds; each competitor plays in at least one fixture per round. The top-ranked competitors in each fixture progress to the next round. As rounds progress, the number of competitors and fixtures decreases. The final round, usually known as the final or cup final, consists of just one fixture; the winner of which is the overall champion. In a single-elimination tournament, only the top-ranked competitors in a fixture progress; in 2-competitor games, only the winner progresses. All other competitors are eliminated. This ensures a winner is decided with the minimum number of fixtures. However, most competitors will be eliminated after relatively few matches; a single bad or unlucky performance can nullify many preceding excellent ones. A double-elimination tournament may be used in 2-competitor games to allow each competitor a single loss without being eliminated from the tournament. All losers from the main bracket enter a losers' bracket, the winner of which plays off against the main bracket's winner. Some formats allow losers to play extra rounds before re-entering the main competition in a later round. Rowing regattas often have repechage rounds for the "fastest losers" from the heats. The winners of these progress, but are at a disadvantage in later rounds owing to the extra effort expended during the repechage. A family of tournament systems that grew from a system devised for the Victorian Football League, the historic predecessor to the Australian Football League (AFL), allow the teams with the best record before the playoffs to lose a game without being eliminated, whereas lesser qualifiers are not. Several of the most prominent leagues in Australia use such a system, such as the AFL and the National Rugby League in rugby league. The A-League of association football also used such a system through its 2011–12 season, but now uses a pure knockout playoff. Similar systems are used in cricket's Indian Premier League and most curling tournaments, and were also used by the Super League of European rugby league before being scrapped after the 2014 season. In athletics meetings, fastest losers may progress in a running event held over several rounds; e.g. the qualifiers for a later round might be the first 4 from each of 6 heats, plus the 8 fastest losers from among the remaining runners. An extreme form of the knockout tournament is the stepladder format where the strongest team (or individual, depending on the sport) is assured of a berth at the final round while the next strongest teams are given byes according to their strength/seeds; for example, in a four team tournament, the fourth and third seed figure in the first round, then the winner goes to the semifinals against the second seed, while the survivor faces the first seed at the final. Four American sports organizations either currently use this format, or have in the past: * Since the mid-1960s, most ten-pin bowling events use a stepladder final, usually involving five bowlers. * Two U.S. college conferences operate a tournament format in basketball that combines two stepladder tournaments into one—that is, both halves of the bracket are organized as stepladder tournaments. The bottom four teams play in the first round; the survivors will face the #3 and #4 seeds, and the winners of those matches take on the top two seeds in the semifinals. This format was adopted by the West Coast Conference for its men's and women's tournaments in 2003, and by the Ohio Valley Conference for both sexes in 2011. Once the WCC expanded to nine teams with the entry of BYU in the 2011–12 academic year, the conference added one round to one half of the bracket for both tournaments starting in 2012. * The now-defunct Women's Professional Soccer used this format in all of its three seasons of existence. For an example of its playoff system, see 2009 Women's Professional Soccer Playoffs. ==Group tournaments== A group tournament, league, division or conference involves all competitors playing a number of ''fixtures'' (again, a fixture is one name for a tournament-match that determines who, out of two or three or more, will advance; a fixture may consist of one or more game-matches between competitors). Points are awarded for each fixture, with competitors ranked based either on total number of points or average points per fixture. Usually each competitor plays an equal number of fixtures, in which case rankings by total points and by average points are equivalent. The English County Championship in cricket did not require an equal number of matches prior to 1963.〔(County Championship history ) Cricinfo〕 In a round-robin tournament, each competitor plays all the others an equal number of times, once in a single round-robin tournament and twice in a double round-robin tournament. This is often seen as producing the most reliable rankings. However, for large numbers of competitors it may require an unfeasibly large number of rounds. A Swiss system tournament attempts to determine a winner reliably, based on a smaller number of fixtures. Fixtures are scheduled one round at a time; a competitor will play another who has a similar record in previous rounds of the tournament. This allows the top (and bottom) competitors to be determined with fewer rounds than a round-robin, though the middle rankings are unreliable. There may be other considerations besides reliability of rankings. In some professional team sports, weaker teams are given an easier slate of fixtures as a form of handicapping. Sometimes schedules are weighted in favour of local derbies or other traditional rivalries. For example, NFL teams play two games against each of the other three teams in their division, one game against half of the other twelve teams in their conference, and one game against a quarter of the sixteen teams in the other conference. American sports are also unusual in providing fixtures between competitors who are, for ranking purposes, in different groups. Another, systematic, example of this was the 2006 Women's Rugby World Cup: each of the teams in Group A played each of the teams in Group B, with the groups ranked separately based on the results. (Groups C and D intertwined similarly.) An elaboration of this system is the Mitchell movement in duplicate bridge, discussed below, where North-South pairs play East-West pairs. (詳細はties are rare or impossible, competitors are typically ranked by number of wins, with ties counting half; each competitors' listings are usually ordered Wins–Losses(–Ties). Where ties are more common, this may be 2 points for a win and 1 for a tie, which is mathematically equivalent but avoids having too many half-points in the listings. These are usually ordered Wins–Ties–Losses. If there are more than two competitors per fixture, points may be ordinal (for example, 3 for first, 2 for second, 1 for third). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「A tournament is a competition involving a relatively large number of competitors, all participating in a sport or game. More specifically, the term may be used in either of two overlapping senses:」の詳細全文を読む スポンサード リンク
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