A play calling system in American football is the specific language and methods used to call plays. Over the years, numerous different systems have existed to communicate, between coaches and players, exactly what the players are supposed to do on any given play. Such systems of play calling are distinguished from philosophies of play calling, which are primarily concerned with how the overall strategy of the game is managed, for example if a team is primarily concerned with running or passing, if a team plays fast or slow, what sorts of passes it throws, etc. Instead, the play calling system is primarily concerned with how plays themselves are actually communicated: how specific plays are named, how players can understand their roles based on the naming of the plays, how such plays are co