In sport, the term "regular season" or "home and away season" refers to the sport's league competition. The regular season is usually similar to a group tournament format: teams are divided into groups, conferences and/or divisions, and each club plays a set number of games against a set number of opponents. In most countries the league is played in a double round-robin format, where every team plays every other team twice, once at their home venue, and once away at the oppositions venue as visitors. The results over all games are accumulated and when every team has completed its full schedule of games, a winner is declared.
In North America, the scheduling is different. Rather than every team playing all others twice, teams usually play more games against local rivals than teams in other parts of the country. For example, the NBA's Los Angeles Lakers will play the Los Angeles Clippers (a team within their division, a subdivision of the conference) four times in a regular season, while both will only play the Boston Celtics, who are in the opposite Eastern Conference, twice. Part of this is due to the vast geographic distances between some teams in North America—measured in a straight line, Los Angeles is 2,606 miles (4,194 kilometers) from Boston, for instance—and a desire to limit travel expenses. In the scheduling system used in the NFL, it is possible for two teams to only meet every four years, and to only have 2 common opponents in a season. Major League Baseball has the most uneven schedules of all the four major North American sports. In MLB the conferences are called leagues instead, but have exactly the same effect as conferences (as with all North American major leagues, leagues, conferences and division are not based on skill, but instead geography, history and rivalries). Teams play 19 games against each of teams in their own division each year but will only play 20 games total against all of the teams in the other league. Because each of the interleague matchups is part of a 3-game series or a 2-game series, teams will play no games at all against most teams from the other league. They play 6 of the 15 teams in the other league, a historically high number (until 1997, interleague play was limited to exhibition matches and the postseason World Series, and thus MLB teams did not play the other league's teams at all).
In Australia, the two largest football leagues, the AFL (Australian rules football) and NRL (rugby league), both grew out of competitions held within a single city (respectively Melbourne and Sydney) and only began expanding to the rest of the country when inexpensive air travel made a national league possible. These leagues use a single table instead of being split into divisions. The term "home and away season" is sometimes used instead of regular season.
Many football leagues in Latin America have a very different system. Because most Latin American countries never had a football cup competition, they instead split their season into two parts, typically known as the Apertura and Clausura (Spanish for "opening" and "closing"). Most countries that use this system, Argentina being one notable example, crown separate league champions for each part of the season, using only league play. A few others, such as Uruguay, crown one champion at the end of a playoff involving top teams from each half of the season. Mexico operates its Apertura and Clausura as separate competitions that both end in playoffs. Brazil have a different system, the season starts with the state championships in January (every Brazilian state have his own championship), these state championships ends in April. The Campeonato Brasileiro Série A itself starts in May and ends in early December, and is played in a double round-robin format in the same way as the European championships.
A system similar to the Apertura and Clausura developed independently in Philippine professional basketball, with formerly two, now three tournaments (called "conferences") in one season, with each conference divided into an "elimination round" (the regular season) and the playoffs in the North American sense. Winning the playoffs is the ultimate goal of every team for every conference; while there is no season championship, winning all conferences within a single season is rare and has only happened five times since 1975, with the two most recent examples occurring in 1996 and 2013–14. The elimination round and playoffs setup has permeated down to the local level and in most team sports, although seasons are not divided into conferences.