Pound

:This article is about the unit of weight. For other uses, see Pound (disambiguation).

Ambiguity

If neither ?avoirdupois? nor ?troy? is specified, nowadays the international pound (avoirdupois) is meant and is by law the only proper definition in the United States, United Kingdom, and Canada; the troy pound has been officially abandoned in the United Kingdom. The valuation of precious metals on U.S. exchanges is specified as dollars per troy ounce, although the fact that the troy ounce is used is usually implied.

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In the colloquial context of vegetable and meat sales within metric countries, a metric pound (500 g) is usually implied.

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Unit of weight

Standards bodies define the pound as a unit of mass, which are the pounds most people in everyday usage use as a unit of weight. When a pound is called a ?unit of weight?, it is usually a unit of mass. In many contexts the word ?weight? is used in its original meaning:

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• In commerce, the terms ?net weight?, troy weight and carat weight actually refer to mass rather than weight. The pounds used for this purpose are units of mass.
• The scientific terms ?molecular weight?, ?atomic weight?, and ?formula weight? all actually refer to mass, which is why some now refer to ?molecular mass?, etc. If a ?pound mole? is used, it is based on the pound as a unit of mass.

Pounds are also used for the force definitions of weight, as well as for other forces, in which the pound force is a unit of force equal to 4.448 newtons. That is the force due to gravity of a pound (avoirdupois) where the acceleration of gravity is 32.17405 ft/s² or 9.80665 m/s². Note, however, that the troy units of weight are never units of force.

Related Topics:
Weight - Pound force - Newton

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