Football is a family of team sports that involve, to varying degrees, kicking a ball to score a goal. Unqualified, the word football normally means the form of football that is the most popular where the word is used. Sports commonly called football include association football ; Australian rules football; Gaelic football; gridiron football ; International rules football; rugby league football; and rugby union football. These various forms of football share, to varying degrees, common origins and are known as "football codes".

During the early modern era, pupils, former pupils and teachers at English public schools developed the rules of football, eventually leading to the first written codes of football most notably the Eton College (1815) and Aldenham school (1825) football rules, and rugby football (1845). British public schools football also directly influenced the rules of association football.