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A sports league is a group of sports teams or individual athletes that compete against each other in a specific sport. At its simplest, it may be a local group of amateur athletes who form teams among themselves and compete on weekends; at its most complex, it can be an international professional league making large amounts of money and involving dozens of teams and thousands of players.
In many cases, organizations that function as leagues are described using a different term, such as conference, leaderboard, or series. This is especially common in individual sports, although the term "league" is sometimes used in amateur individual sports such as golf.
The term "league" is also sometimes applied to competitions that would more traditionally be called tournaments, such as the UEFA Champions League, which is organized with multiple small round-robin competitions followed by a single elimination tournament to choose an overall winner.
Leagues and league systems 
"League" and its synonyms may be used to encompass either a single competition or a related group of competitions. In the United States, leagues are often divided into subdivisions on historical or geographical lines. These may be referred to as conferences or divisions, as with the National Football Conference and American Football Conference in the National Football League, or the Eastern and Western Conferences of the National Basketball Association and National Hockey League. The NFL's "AFC" was formed largely from the remnants of the American Football League, though it also contains three original NFL teams and three expansion teams.
Baseball has a unique nomenclature, with "Major League Baseball" the name of the overall grouping of 30 teams in two "major leagues," the American League and the older National League. These are titled leagues rather than conferences for several reasons. The National League predates the American by 25 years and was considered a "major" league in comparison to its early competitors, and in a sense it simply extended this recognition to the AL, the only league of similar financial clout. In addition, the leagues played no interlocking schedule of any kind until 1995, and then added only a small amount of interleague play, with the main AL-NL competition occurring between their champions in the World Series. Thus the two leagues played mostly separate competitions within the larger framework of MLB. Finally, until 2000, they were actually separate legal entities, unlike the conferences of other leagues. Nippon Professional Baseball in Japan has a similar history, with the Central League and Pacific League not originally founded together.
Due to this naming custom, it is common to use slightly different terms to discuss MLB. Where someone might refer to "the best quarterback in the league" and be understood to mean the overall NFL, a similar mention of "the best outfielder in the league" is almost always a reference to the American or National League, and "all of baseball" or similar is used to denote the larger status. Each of the major leagues also has its own set of awards to recognize the separation between the two, which means there are two MVPs, two Cy Young winners, etc. And since its name is constructed differently—a description of the status of two leagues rather than the title of one—it is common to hear "MLB" without "the" attached to it, as in "the most home runs in MLB this year," since one would not say "the Major League Baseball."
In all four of the major North American sports, regardless of whether the subsets are called "league" or "conference," they each have their own subsets, all of which are called "divisions." These are geographically based, and teams play their divisional opponents more than any others, especially in the NFL and MLB.
In other parts of the world, and especially in association football, where promotion and relegation is common, the term "league" may be used to refer both to a league system, a group of leagues that are tied together in a hierarchical fashion by promotion and relegation, and to the individual leagues within the league system. For example, the Football League in England and the Bundesliga in Germany are both association football league systems.
League organization 
The common thread between all sports leagues is a structure that allows teams or individuals to compete against each other in a nonrandom order on a set schedule, usually called a "season," with the results of the individual competitions being used to name an overall champion.
A league championship may be contested in a number of ways. Each team may play every other team a certain number of times in a round-robin tournament. Usually, teams play equal number of games or matches at their own stadium and at other teams', because home advantage is a major factor in many sports. When teams competing for a tournament championship do not play the same teams the same number of times, it is known as an unbalanced schedule.
In such a set-up, the team with the best record becomes champion, based on either a strict win-loss-tie system or on a points system where a certain number of points are awarded for a win, loss, or tie, while bonus points might also be added for teams meeting various criteria. Many leagues also use playoffs, where after teams compete in a regular season in a league format, the top teams (possibly determined by conference or division) advance to the playoffs. In some such leagues having the best regular season record is relatively unimportant, though top-seeded teams in some leagues, such as the NFL, can gain byes to later rounds of the playoffs, and teams finishing with the best records usually have the advantage of playing the weakest teams that have advanced to the playoffs.
Alternatives to traditional league organization 
While round-robin and modified round-robin competitions are the most common form of league organization, there are a number of ways to organize a sporting competition, almost all of which may be described as a "league". Many sports organizations fall on a continuum between a total lack of organization, as in a pick-up game, and a formal league such as is common at the highest level of professional team sports.
Non-league sports 
The simplest form of competition is to allow teams to play each other whenever they see fit. In some sports, such as horse racing, the main goal of the entrants is to win individual purses, and there is little or no ranking or competition outside of winning certain major races. A small amount of league organization may be imposed on these non-league sports by way of a series or tournament tying several individual events together, such as the Triple Crown.
Even in team sports that normally use a traditional league format, some teams often exist outside of any league; these teams are generally known as barnstorming teams and either schedule games against local professional or amateur competition or bring their own competition, such as the barnstorming Harlem Globetrotters did when they toured with the Washington Generals. As with the Globetrotters, barnstorming teams sometimes emphasize spectacle over athletic competition.
In Europe, the term "cup competition" is used to describe single elimination or knock-out tournaments, where the pairing of teams in each round is determined by a "draw" (see for example, the FA Cup in England), to distinguish it from league competition, in which every club in the league or division plays the other teams a pre-determined number of times in a season, usually on a home and away basis.
Further, in England, the term non-league football is used for historical reasons to describe association football teams that play in organized leagues, but not in the Football League or Premier League, the two highest levels of competition in that sport in that country.
Independent baseball is used similarly in the United States to describe baseball teams that play in leagues other than those sanctioned by Major League Baseball. These teams do play in leagues and should not be confused with barnstorming teams that play truly non-league schedules.
Rankings and leaderboards 
Individual sports often use an alternative type of league organization where competitors are ranked against each other. In the simplest cases, such as boxing, the rankings mean little and the major competition is to crown a champion in a title fight.
In other sports, the rankings and leaderboards gain importance when they are used in seeding tournaments. In some cases, as in NASCAR or the PGA Tour, points are assigned to individual competitions and the resulting points are used to determine a champion at the end of each season. While not usually referred to as "leagues," these season-long competitions with set events are very similar to league structures in team sports.
Conferences and informal leagues 
American college sports are traditionally organized into groups of teams known as "conferences." These conferences ordinarily keep league tables and crown champions within the conference, as other sports leagues do, but the individual school also schedule a certain number of "non-conference" games that are organized independently between two schools in different conferences, or between a conference team and a non-conference team. Also, national championships in some college sports are determined by a ranking or playoff system that is independent of the individual conferences.
Round-robin sports leagues 
Most major professional team sports play some form of round-robin schedule, where the goal is for each team to play a relatively balanced schedule with each other team in the league or in its league subdivision. Within this structure, there are a few significant differences between leagues, a few of which are set forth below.
Single-table versus unbalanced schedule 
The simplest way to organize a sports league, and still one of the most common, is in a double round-robin format where each team plays each other team twice, once at home and once away. This ensures that every team plays an equally difficult schedule and that no team has undue home field advantage. This organization is still used in many team sports around the world.
One potential drawback of this simple double round-robin format is that the number of teams in the league determines the schedule. Larger leagues may not be able to play as many games as such a system would require, and smaller leagues may want more games. One solution is to play an unbalanced schedule, with some teams playing additional games against some other teams; this is the way Major League Soccer has traditionally been scheduled, with the additional games being played against local rivals. Some leagues also break the league into subunits, often known as "divisions" and "conferences," each of which may itself play a balanced or unbalanced schedule.
Cups, tournaments and playoffs 
Many sports leagues also participate in a single-elimination tournament each year. In the United States, Mexico, and some other countries, these tournaments are commonly called "playoffs" and are played at the end of the season, with the teams qualifying for the playoffs based on their performance during the season. In Europe, "cup" competitions are more common, with all teams playing in a single-elimination tournament that takes place during and parallel with the regular season.
See also 
- League club
- League system
- Promotion and relegation
- Group tournaments
- Regulation of sport
- List of professional sports leagues
- Professional sports league organization
- Major professional sports leagues in the United States and Canada
- List of college athletic conferences
- List of developmental and minor sports leagues
- List of high school sports conferences
- List of defunct sports leagues
- List of sports attendance figures
- List of attendance figures at domestic professional sports leagues
- Outline of sports#General sports concepts
Further reading 
- Cain, Louis P. and Haddock, David D.; 2005; 'Similar Economic Histories, Different Industrial Structures: Transatlantic Contrasts in the Evolution of Professional Sports Leagues'; Journal of Economic History 65 (4); pp1116–1147