The avoirdupois (pronounced /ˌævərdəˈpɔɪz/; French pronunciation: [avwaʁdypwɑ]) system is a system of weights (or, properly, mass) based on a pound of sixteen ounces. It is the everyday system of weight used in the United States, and is still widely used to varying degrees by many people in Canada, the United Kingdom, and some other former British colonies despite the official adoption of the metric systemcitation needed. An alternate system of mass is generally used for precious materials, Troy weight. Contents 1 History of the term 2 Original forms 3 British adaptation 4 American customary system 5 Internationalization 6 See also History of the term Chart showing the relationships of English weight measures.

The word avoirdupois is from Old French aveir de peis (later avoir de pois), literally "goods of weight" (Old French aveir, "property, goods", also "to have", comes from the Latin habere, "to have, to hold, to possess property"; de = "from", cf. Latin; peis = "weight", from Latin pensum). This term originally referred to a class of merchandise: aveir de peis, "goods of weight", things that were sold in bulk and were weighed on large steelyards or balances. Only later did it become identified with a particular system of units used to weigh such merchandise. The imaginative orthography of the day and the passage of the term through a series of languages (Latin, Anglo-French and English) has left many variants of the term, such as haberty-poie and haber de peyse. (The Norman peis became the Parisian pois. In the 17th century de was replaced with du.) Original forms

These are the units in their original French forms: Table of mass units Unit Relative value Notes dram or drachm 1⁄256 1⁄16 once once 1⁄16 livre 1 quintal 100 tonne 2,000 20 quintaux Note: The plural of quintal is quintaux. British adaptation When people in the United Kingdom began to use this system they included the stone, which was eventually defined as fourteen avoirdupois pounds. The quarter, hundredweight, and ton were altered, respectively, to 28 lb, 112 lb, and 2,240 lb in order for masses to be easily converted between them and stones. The following are the units in the British or imperial adaptation of the avoirdupois system: Table of mass units Unit Relative value Metric value Notes dram or drachm 1⁄256 ≈ 1.772 g 1⁄16 oz ounce (oz) 1⁄16 ≈ 28.35 g 16 dr pound (lb) 1 ≈ 453.6 g 16 oz stone (st) 14 ≈ 6.350 kg 1⁄2 qtr quarter (qtr) 28 ≈ 12.70 kg 2 st hundredweight (cwt) 112 ≈ 50.80 kg 4 qtr ton (t) or long ton (l. tn.) 2,240 ≈ 1,016 kg 20 cwt

Note: The plural form of the unit stone is either stone or stones, but stone is most frequently used. American customary system Main article: United States customary units The thirteen British colonies in North America used the avoirdupois system. But they continued to use the British system as it was, without the evolution that was occurring in Britain in the use of the stone unit. In 1824 there was landmark new weights and measures legislation in the United Kingdom that the United States did not adopt. In the United States, quarters, hundredweights, and tons remain defined as 25, 100, and 2,000 lb respectively. The quarter is now virtually unused, as is the hundredweight outside of agriculture and commodities. If disambiguation is required, then they are referred to as the smaller "short" units in the United States, as opposed to the larger British "long" units. Grains are used worldwide for measuring gunpowder and smokeless powder charges. Historically, the dram has also been used worldwide for measuring gunpowder charges, for measuring powder charges for shotguns and large blackpowder rifles. Table of mass units Unit Relative value Metric value Notes grain (gr) 1⁄7000 ≈ 64.80 mg 1⁄7000 lb dram (dr) 1⁄256 ≈ 1.772 g 1⁄16 oz ounce (oz) 1⁄16 ≈ 28.35 g 16 dr pound (lb) 1 ≈ 453.6 g 16 oz quarter (qtr) 25 ≈ 11.34 kg 25 lb hundredweight (cwt) 100 ≈ 45.36 kg 4 qtr ton (t) or short ton (sh. tn.) 2,000 ≈ 907.2 kg 20 cwt Internationalization

In the avoirdupois system, all units are multiples or fractions of the pound, which is now defined as 0.45359237 kg in most of the English-speaking world since 1959. (See the Mendenhall Order for references.) Due to the ambiguous meanings of "weight" as referring to both mass and force, it is sometimes erroneously asserted that the pound is only a unit of force.citation needed However, as defined above the pound is a unit of mass, which agrees with common usage. Also see pound-force and pound-mass. See also Look up avoirdupois in Wiktionary, the free dictionary. Wikisource has the text of the 1911 Encyclopædia Britannica article Avoirdupois. Apothecaries' system French units of measurement Imperial unit Troy weight United States customary units v · d · eSystems of measurement Metric systems

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