In Canada, the term "football" may refer to Canadian football and American football collectively, or to either sport specifically, depending on context; outside of Canada, the term Canadian football is used exclusively to describe this sport, even in the United States (the term "gridiron football" more rarely, "North American football" is also used worldwide as well to refer to both sports collectively). The two sports have shared origins and are closely related but have some key differences, and both sports had their modern rules developed independently from each other.