Gridiron football

Gridiron football is a family of football codes played on rectangular fields marked with parallel lines. Its best-known forms are American football and Canadian football.

Line of scrimmage: The transverse line marking where a play begins and separating opposing teams before the snap. It organizes the start of plays across both major gridiron codes.
American football: A gridiron football code played mainly in the United States, with 11 players per team on the field. It is the most widely followed member of the gridiron family.
Rugby football: A family of football games descended from rules developed at Rugby School in England. Gridiron football emerged from rugby-style games played in North America.
National Football League: The leading professional American football league, comprising teams in the United States. The NFL is the most prominent professional competition in the American code.
Down (gridiron football): A team’s opportunity to run a play before the ball becomes dead or possession changes. Downs structure possession and advancement in American and Canadian football.
Canadian football: A gridiron football code played mainly in Canada, with 12 players per team on the field. Its larger field and distinct rules make it the other major gridiron code.
Walter Camp: An American football coach and rules innovator who helped establish the game’s early form. His rule changes, including the line of scrimmage, shaped the American code.
Canadian Football League: The leading professional Canadian football league, with teams based in Canada. The CFL maintains a distinct professional competition for the Canadian code.
Forward pass: A throw that sends the ball toward the opponent’s end of the field. The forward pass is a defining offensive option in modern gridiron codes.
Rugby union: A rugby football code in which teams of 15 contest possession using running, kicking, and backward passing. It shares rugby ancestry with gridiron football but retains different possession and passing rules.

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