According to the National Park Sevice, "In North America, both 'bison' and 'buffalo' refer to the American bison (Bison bison). Generally, 'buffalo' is used informally; 'bison' is preferred for more formal or scientific purposes. Historians believe that the term 'buffalo' grew from the French word for beef, 'boeuf.' Some people insist that the term 'buffalo' is incorrect because the 'true' buffalo exist on other continents and are only distant relatives."