Some of the many different games known as football. 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, more commonly known as just "football" or "soccer". 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; 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 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;
• goals and/or points resulting from players putting the ball between two goalposts
• 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
• 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/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.

Etymology

main: Football (word) While it is widely believed that the word "football" (or "foot ball") originated in reference to the action of the foot kicking a ball, there is a rival explanation, which has it that football originally referred to a variety of games in medieval Europe, which were played on foot. These games were usually played by peasants, as opposed to the horse-riding sports often played by aristocrats. While there is no conclusive evidence for this explanation, 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.

Ancient games

thumb|150px|left|Ancient Greek football player balancing the ball. Depiction on an Attic Lekythos. The Ancient Greeks and Romans are known to have played many ball games, some of which involved the use of the feet. The Roman game harpastum is believed to have been adapted from a team game known as "επισκυρος" (episkyros) or phaininda, which is mentioned by a Greek playwright, Antiphanes (388–311 BC) and later referred to by the Christian theologian Clement of Alexandria (c.150-c.215 AD). The Roman politician Cicero (106-43 BC) describes the case of a man who was killed whilst having a shave when a ball was kicked into a barber's shop. These games appear to have resembled rugby football. Roman ball games already knew the air-filled ball, the follis.