The game of football is any of several similar team sports, of similar origins 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, more commonly known as just "football" or "soccer". Unqualified, the word football applies to whichever form of football is the most popular in the regional context in which the word appears, including American football, Australian rules football, Canadian football, Gaelic football, rugby league, rugby union and other related games. These variations are known as "codes."

Common elements
The various codes of football share the following common elements:
* Two teams of usually between 11 and 18 players; some variations that have fewer players (five or more per team) are also popular.
* A clearly defined area in which to play the game.
* Scoring goals 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.
* Goals or points resulting from players putting the ball between two goalposts.
* The goal or line being defended by the opposing team.
* Players being required to move the ball—depending on the code—by kicking, carrying, or hand-passing the ball.
* Players using only their body to move the ball.

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 or make a fair catch.

Peoples from around the world have played games which involved kicking or carrying a ball, since ancient times. However, most of the modern codes of football have their origins in England.

Etymology
While it is widely assumed that the word "football" (or "foot ball") references the action of the foot kicking a ball, there is a historical explanation, which is that football originally referred to a variety of games in medieval Europe, which were played on foot.[2] These games were usually played by peasants, as opposed to the horse-riding sports (such as polo) often played by aristocrats. There is no conclusive evidence for either explanation, and the word football has always implied a variety of games played on foot, not just those that involved kicking a ball. In some cases, the word football has even been applied to games which have specifically outlawed kicking the ball.

Use of the word "football"
The word "football", when used in reference to a specific game can mean any one of those described above. Because of this, much friendly controversy has occurred over the term football, primarily because it is used in different ways in different parts of the English-speaking world. Most often, the word "football" is used to refer to the code of football that is considered dominant within a particular region. So, effectively, what the word "football" means usually depends on where one says it.
Players assemble at the line of scrimmage in an American football game.

Association football has generally been known as "soccer" in the U.S, Canada, Ireland, Australia and New Zealand where other codes of football are dominant, while in francophone Quebec, where Canadian football is more popular, the sport of association football is known as le soccer[68] and the Canadian code as football. Of the 45 national FIFA affiliates in which English is an official or primary language, almost all now use "football" in their organizations' official names, although Canada and the United States the national football organizations continue to use the name "Soccer" in their titles, and several others have only recently "normalized" to using "Football", including:
* Australia's association football governing body changed its name in 2007 from using "soccer" to "football"
* New Zealand also changed in 2007, saying "the international game is called football".
* Samoa changed from "Samoa Football (Soccer) Federation" to "Football Federation Samoa" in 2009