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English units of measurement

English units of measurement, principal system of weights and measures used in a few nations, the only major industrial one being the United States. It actually consists of two related systems—the U.S. Customary System of units, used in the United States and dependencies, and the British Imperial System. The names of the units and the relationships between them are generally the same in both systems, but the sizes of the units differ, sometimes considerably.

Customary Units of Weights and Measures

Units of Weight

The pound (lb) is the basic unit of weight (which is proportional to mass). Within the English units of measurement there are three different systems of weights. In the avoirdupois system, the most widely used of the three, the pound is divided into 16 ounces (oz) and the ounce into 16 drams. The ton, used to measure large masses, is equal to 2,000 lb (short ton) or 2,240 lb (long ton). In Great Britain the stone, equal to 14 lb, is also used. The troy system (named for Troyes, France, where it is said to have originated) is used only for precious metals. The troy pound is divided into 12 ounces and the troy ounce into 20 pennyweights or 480 grains; the troy pound is thus 5,760 grains. The grain is also a unit in the avoirdupois system, 1 avoirdupois pound being 7,000 grains, so that the troy pound is 5,760/7,000 of an avoirdupois pound. Apothecaries' weights are based on troy weights; in addition to the pound, ounce, and grain, which are equal to the troy units of the same name, other units are the dram (1/8 oz) and the scruple (1/24 oz or 1/3 dram).

Units of Length and Area

The basic unit of length is the yard (yd); fractions of the yard are the inch (1/36 yd) and the foot (1/3 yd), and commonly used multiples are the rod (51-2 yd), the furlong (220 yd), and the mile (1,760 yd). The acre, equal to 4,840 square yards or 160 square rods, is used for measuring land area.

Units of Liquid Measure

For liquid measure, or liquid capacity, the basic unit is the gallon, which is divided into 4 quarts, 8 pints, or 32 gills. The U.S. gallon, or wine gallon, is 231 cubic inches (cu in.); the British imperial gallon is the volume of 10 lb of pure water at 62℉ and is equal to 277.42 cu in. The British units of liquid capacity are thus about 20% larger than the corresponding American units. The U.S. fluid ounce is 1/16 of a U.S. pint; the British unit of the same name is 1/20 of an imperial pint and is thus slightly smaller than the U.S. fluid ounce.

Units of Dry Measure

For dry measure, or dry capacity, the basic unit is the bushel, which is divided into 4 pecks, 32 dry quarts, or 64 dry pints. The U.S. bushel, or Winchester bushel, is 2,150.42 cu in. and is about 3% smaller than the British imperial bushel of 2,219.36 cu in., with a similar difference existing between U.S. and British subdivisions. The barrel is a unit for measuring the capacity of larger quantities and has various legal definitions depending on the quantity being measured, the most common value being 105 dry quarts.

Differences between American and British Systems

Many American units of weights and measures are based on units in use in Great Britain before 1824, when the British Imperial System was established. Since the Mendenhall Order of 1893, the U.S. yard and pound and all other units derived from them have been defined in terms of the metric units of length and mass, the meter and the kilogram; thus, there was no longer any direct relationship between American units and British units of the same name. In 1959 an international agreement was reached among English-speaking nations to use the same metric equivalents for the yard and pound for purposes of science and technology; these values are 1 yd=0.9144 meter (m) and 1 lb=0.45359237 kilogram (kg). In the United States, the older definition of the yard as 3,600/3,937 m has continued to be used in many instances for surveying, the corresponding foot (1,200/3,937 m) being known as the survey foot; the survey foot will become obsolete in 2023.

The English units of measurement have many drawbacks: the complexity of converting from one unit to another, the differences between American and British units, the use of the same name for different units (e.g., ounce for both weight and liquid capacity, quart and pint for both liquid and dry capacity), and the existence of three different systems of weights (avoirdupois, troy, and apothecaries'). Because of these disadvantages and because of the wide use of the much simpler metric system in most other parts of the world, there have been proposals to do away with the U.S. Customary System and replace it with the metric system.


See L. J. Chisholm, Units of Weights and Measure: International and U.S. Customary (U.S. National Bureau of Standards, 1967).


leopard, large carnivore of the cat family, Panthera pardus, widely distributed in Africa and Asia. It is commonly yellow, buff, or gray, patterned with black spots and rings. The rings, unlike those of the New World jaguar, never have spots inside them. Black leopards are commonly called panthers, a name sometimes used for all leopards. They are not a distinct species but merely a color variant caused by melanism, or excessive pigmentation. Close inspection reveals the typical spotting, which is obscured by the darkness of the background.

Leopards are somewhat smaller than lions and tigers; the largest males are about 7 ft (2.3 m) long, including the 3-ft (90-cm) tail. Leopards are solitary, largely nocturnal, and good climbers; they hunt both on the ground and in trees. They prey mostly on small animals such as monkeys, rodents, and birds. Leopards are found in much of Africa south of the Sahara and in parts of Asia from Israel to Korea and Indonesia. They are listed as threatened or endangered throughout their range, owing primarily to loss of their natural habitat and to illegal killing for Asian folk medicine.

A related species is the snow leopard, or ounce, Uncia uncia or P. uncia, which replaces ordinary leopards in the high mountains of Central Asia. It has long whitish fur and diffuse spotting. In summer, when the mountain animals on which it preys range to high pastures, the snow leopard may climb to an altitude of 13,000 ft (3,900 m). It usually hunts at dusk or at night. More distantly related are the clouded leopards, Neofelis nebulosa of SE Asia and Neofelis diardi (Sunda clouded leopard) of Borneo and Sumatra; they were considered a single species until the early 21st cent. The coat is more tawny and lighter in the clouded leopard, more gray and darker in the Sunda clouded leopard. Both have coats strikingly marked with black and brown; there are stripes on the face and tail, spots on the limbs, and rosettes on the body. The tail is exceptionally long and heavy and is thickly furred. Forest dwellers, clouded leopards are nocturnal and arboreal in their habits. Unlike the leopard, both the snow and clouded leopards do not roar. The clouded leopard is an endangered species; the snow leopard is considered vulnerable.

Leopards are classified in the phylum Chordata, subphylum Vertebrata, class Mammalia, order Carnivora, family Felidae.

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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



(1) A unit of weight in the English system of measures. One ounce equals 16 drams = 437.5 grains = 28.3495 g.

(2) A unit of apothecaries’ weight. The apothecaries’ ounce contains 8 drams or 24 scruples; the Russian apothecaries’ ounce was equal to 29.860 g. In the English system of measures, the apothecaries’ ounce, as well as the troy ounce (a measure of weight for precious metals), is equal to 31.1035 g.

(3) Fluidounce, a measure of volume, equivalent to 8 fluidrams. The fluid ounce corresponds to 29.5737 cm3 in the USA or to 28.413 cm3 in Great Britain.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


A unit of mass in avoirdupois measure equal to ¹⁄₁₆ pound or to approximately 0.0283495 kilogram. Abbreviated oz.
A unit of mass in either troy or apothecaries' measure equal to 480 grains or exactly 0.0311034768 kilogram. Also known as apothecaries' ounce or troy ounce (abbreviations are oz ap and oz t in the United States, and oz apoth and oz tr in the United Kingdom).
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


1. a unit of weight equal to one sixteenth of a pound (avoirdupois); 1 ounce is equal to 437.5 grains or 28.349 grams
2. a unit of weight equal to one twelfth of a Troy or Apothecaries' pound; 1 ounce is equal to 480 grains or 31.103 grams
3. short for fluid ounce
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
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