Regular season

In an organized sports league, a season is the portion of one year in which regulated games of the sport are in session. For example, in Major League Baseball, one season lasts approximately from April 1 through October 1; in association football, it is generally from August until May (although in some countries, especially those in Scandinavia, the season starts in the spring and finishes in the autumn due to the weather conditions encountered during the winter). A year can often be broken up into several distinct sections (sometimes themselves called seasons). These are:

Pre-season
Most team sports have a period of training to recover fitness levels, followed by exhibition games or friendly matches prior to the start of their regular seasons ("pre-season training" and "pre-season" games). The game results do not count in the season standings of the teams, so they serve conveniently to test player candidates and to practice teamwork under game conditions. They may be used to promote the team effectively both at home and elsewhere. For some teams a pre-season overseas tour may be profitable, even lucrative. For some leagues, overseas games may promote their sport or their league to new audiences.

Regular season
The terms season (UK), regular season (North America) and home and away season (Australia) are used to denote the time when the bulk of games are played. In Australia and North America, it is common for the teams to play a regular season and use the results to seed a post-season playoff tournament. Elsewhere, league and/or cup competitions are played at the same time during the "season". Depending on the sport and league, all teams may or may not play against each other. All teams usually play the same number of games, and will play half the matches at their home ground or arena and the other half away at opponents' venues.

Post-season
Many sports leagues have playoffs that occur after the regular season is complete. A subset of the teams enter into a playoff tournament, generally a pre-determined number with better overall records (more wins, fewer losses) during the regular season. There are many variations used to determine the champion, the league's top prize.

Off-season
The off-season, vacation time, or close season is the time of year when there is no official competition. Although upper management continues to work, the athletes will take much vacation time off. Also, various events such as drafts, transfers and important off-season free agent signings occur. Generally, most athletes stay in shape during the off-season in preparation for the next season. Certain new rules in the league may be made during this time, and will become enforced during the next regular season.

Seasons by league
The table represents typical seasons for some leagues by month. Blank or white denotes off-season and pre-season months and solid colors mark the rest of the year. Leagues in the same sport use the same color.
 * "Q" denotes pre-competition qualifiers
 * "S" denotes the start of the regular-season.
 * "P" denotes playoff(s)/postseason/knockout stages.
 * "F" denotes Final(s).