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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).

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 It might be outdated or ideologically biased.



(drachm; Russian drakhma, from Greek drachme).

(1) A unit in the now outmoded system of apothecaries’ weights. An apothecaries’ dram was one-eighth of an ounce and contained three scruples; the Russian apothecaries’ dram was the equivalent of 3.732 g. In the English system of measurement an apothecaries’ dram equaled 3.888 g.

(2) A fluidram, a measure of displacement used in the USA, equal to 3.6966 milliliters.

(3) In the avoirdupois system, a measure of weight equaling one-sixteenth of an ounce, 1.772 g.

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


A unit of mass, used in the apothecaries' system of mass units, equal to ⅛ apothecaries' ounce or 60 grains or 3.8879346 grams. Also known as apothecaries' dram (dram ap); drachm (British).
A unit of mass, formerly used in the United Kingdom, equal to ¹⁄₁₆ ounce (avoirdupois) or approximately 1.77185 grams. Abbreviated dr.


(computer science)
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


1. one sixteenth of an ounce (avoirdupois). 1 dram is equivalent to 0.0018 kilogram
2. US one eighth of an apothecaries' ounce; 60 grains. 1 dram is equivalent to 0.0039 kilogram
3. a small amount of an alcoholic drink, esp a spirit; tot
4. the standard monetary unit of Armenia, divided into 100 lumas
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005


This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)

dynamic RAM

The most common type of computer memory and generally available today in the form of synchronous dynamic RAM chips (see SDRAM). Most all volatile memory is dynamic RAM because it uses only one transistor and one storage capacitor for each bit. It is denser and much less costly than "static RAM," its faster counterpart.

Dynamic RAM Is a Total Loser
Unlike non-volatile firmware chips (flash, ROM, EEPROM, etc.), which hold their contents when the power is turned off, both dynamic RAM (DRAM) and static RAM (SRAM) require constant power.

The capacitors in a dynamic RAM chip are electrical storage tanks that do a poor job of holding a charge. They constantly leak, and the memory chip would lose its content were it not for the refresh circuitry that continuously re-energizes the capacitors approximately 15 times per second.

In 1968, dynamic RAM was patented by IBM, and the first commercial chips came from Intel and Mostek in the early 1970s with a capacity of 1,000 bits. See static RAM and memory types.

A Dynamic RAM Cell
DRAM cells are very simple. The combination of voltage on the row and column lines charges a capacitor. The only problem is that the capacitors keep losing their charges, and the bits must be read and re-written to the same state several times each second.

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