The stone was defined in British legislation as being a unit of either "weight or mass" equal to 14 [avoirdupois] pounds (6.35029318 kilograms). It was also formerly used in several Commonwealth countries. Eight stone make a hundredweight in the Imperial system. When used as the unit of measurement, the plural form of stone is correctly stone (as in, "11 stone"), though stones is sometimes used, but not usually by British natives. The abbreviation is st. When describing the units, the correct plural is stones (as in, "Please enter your weight in stones and pounds").