AVOIRDUPOIS WEIGHT

(from French avoir de pois, goods of weight), traditional European system of weight incorporated into the British Imperial System and the U.S. Customary System of weights and measures. The avoirdupois pound is divided into 16 ounces, the ounce into 16 drams; the pound is equivalent to 7,000 grains and thus to about 1.22 apothecaries' or troy pounds. Since 1959 the avoirdupois pound has been officially defined in most English-speaking countries as 0.45359237 kilogram. The avoirdupois pound and its subdivisions originated in the European Middle Ages for weighing goods other than precious metals (for which troy weight was used) and drugs and medicines (for which apothecaries' weight was used).