Football is the word given to a number of similar team sports, all of which involve (to varying degrees) kicking a ball with the foot in an attempt to score a goal. The most popular of these sports worldwide is association football, also known as "soccer" and most commonly just "football". The English language word "football" is also applied to "gridiron football" (a name associated with the North American sports, especially American football and Canadian football), Australian football, Gaelic football, rugby football (rugby league and rugby union), and related games. Each of these codes (specific sets of rules, or the games defined by them) is referred to as "football".
These games involve:
* Two teams of usually between 11 and 18 players. Note that versions with fewer players have varying degrees of popularity:
o Six-man, eight-man, and nine-man football, derived from American football, are also played mainly at scholastic level in less-populated parts of the United States. Small schools in the Canadian province of Saskatchewan also play nine-man football, derived from the country's own code.
o Rugby sevens, a version of rugby union with seven players per side instead of 15, is especially well-developed, with its own World Cup, a prominent annual international competition, and an entrenched position in the Commonwealth Games.
o Although the sevens format also exists in rugby league, a different abbreviated format, rugby league nines, is more popular.
* a clearly defined area in which to play the game;
* scoring goals and/or points, by moving the ball to an opposing team's end of the field and either into a goal area, or over a line;
* the goal and/or line being defended by the opposing team;
* players being required to move the ball—depending on the code—by kicking, carrying and/or hand passing the ball; and
* goals and/or points resulting from players putting the ball between two goalposts.
In most codes, there are rules restricting the movement of players offside, and players scoring a goal must put the ball either under or over a crossbar between the goalposts. Other features common to several football codes include: points being mostly scored by players carrying the ball across the goal line and; players receiving a free kick after they take a mark/make a fair catch.
Peoples from around the world have played games which involved kicking and/or carrying a ball, since ancient times. However, most of the modern codes of football have their origins in England.