Football is the name of several 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". However the word football is applied to whichever form of football became most popular in each particular part of the world. Hence the English language word "football" is applied to "gridiron football" (a name associated with the North American sports, especially American football and Canadian football), Australian football, Gaelic football, rugby league, rugby union, and related games. These rule variations are known as "codes."