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Troy weight, avoirdupois weight, and apothecaries' weight are all built from the same basic unit, the grain, which is the same in all three systems. However, while each system has some overlap in the names of their units of measure (all have ounces and pounds), the relationship between the grain and these other units within each system varies.
An ounce-force is 1 ⁄ 16 of a pound-force, or about 0.2780139 newtons. It is defined as the force exerted by a mass of one avoirdupois ounce under standard gravity (at the surface of the earth, its weight). The "ounce" in "ounce-force" is equivalent to an avoirdupois ounce; ounce-force is a measurement of force using avoirdupois ounces.
Another difference arose when Britain abolished the troy pound (373.241 7216 g) on 1 January 1879, leaving only the troy ounce (31.103 4768 g) and its decimal subdivisions, whereas the troy pound (of 12 troy ounces) and pennyweight are still legal in the United States, although they are no longer widely used.
The apothecaries and troy pounds are divided into 12 ounces (of 480 grains) while the avoirdupois pound has 16 ounces (of 437.5 grains). The unit of volume, the gallon, has different values in the United States and in the United Kingdom – the US fluid gallon being about 0.83 imperial gallons and the US dry gallon being about 0.97 imperial ...
The pound or pound-mass is a unit of mass used in both the British imperial and United States customary systems of measurement.Various definitions have been used; the most common today is the international avoirdupois pound, which is legally defined as exactly 0.453 592 37 kilograms, and which is divided into 16 avoirdupois ounces. [1]
The troy weight units are the grain, the pennyweight (24 grains), the troy ounce (20 pennyweights), and the troy pound (12 troy ounces). The troy grain is equal to the grain unit of the avoirdupois system, but the troy ounce is heavier than the avoirdupois ounce, and the troy pound is lighter than the avoirdupois pound. Legally, one troy ounce ...
Weight is measured in ounces and pounds (avoirdupois) as in the U.S. Volume is measured in imperial gallons, quarts, pints, fluid ounces, fluid drachms, and minims. The imperial gallon was originally defined as 10 pounds (4.5359 kg) of water in 1824, and refined as exactly 4.54609 litres in 1985.
The confusing variety of definitions and conversions for pounds and ounces is covered elsewhere in a table of pound definitions. To unify all weight systems used by apothecaries, the Irish pharmacopœia of 1850 introduced a new variant of the apothecaries' system which subdivided a new apothecaries' pound of 12 avoirdupois ounces instead of the ...