acre (used as a unit of length) various historical references mention "acre" as a unit of length,īut there has never been any official definition of such a unit. North German and Dutch morgen, south GermanĪnd Czech jitro. Similar units include the French journal, Is typical in being defined as a day's work but unusual in not being visualizedĪs the area of a square. Among traditional European land area units, the acre Meters (the area of a square 100 meters on each side).
In metric countries the unit corresponding to theĪcre is the hectare, which is 10 000 square There are exactly 640Īcres in a square mile. Square rods, 43 560 square feet or 4840 square yards. Ninth century it was generally understood to be the area of a field one furlong In England at least as early as the eighth century, and by the end of the The acre was originally definedĪs the area that could be plowed in a day by a yoke of oxen. "Acre," an Old English word meaning a field, is derived from the Latin agerĪnd Greek agros, also meaning a field. acre (ac or A) a unit of area used for measuring real estate in English-speaking countries. The CGS acoustic ohm equals 10 5 MKS acoustic ohms. System, the acoustic ohm is equal to the SI unit,ġ pascal second per cubic meter (Pa System, the acoustic ohm equals 1 microbar second per cubic centimeter (µbar What units are used to measure pressure and time. Unfortunately, the result is often stated in "acoustic ohms" no matter The pressure of the sound wave at the surface divided by the volume velocity. The sound resistance across a surface in a given medium is defined to be Name by analogy with electric resistance, which is measured in ohms. acoustic ohm any one of several units measuring sound resistance. ACI a symbol for the "anatomical Chinese inch" or t'sun Minute", "actual cubic feet per hour", "actual cubic feet per day", and "actualĬubic inches per minute." Many similar abbreviations are in use. accm, acfm, acfh, acfd, acim (etc.) symbols for "actual cubic centimeters per minute", "actual cubic feet per schools, generally equal to 9 months beginning inĪugust or September. abv, abw symbols for alcohol by volume and alcohol by weight. Note that AU is also used in astronomy as a symbolįor the astonomical unit (see below). If the absorbance is 1.0ĪU then 10% of the light is transmitted at 2.0 AU only 1% of the light is To a reduction in transmittance by a factor of 10. An increase in absorbance of 1.0 AU corresponds Of light transmitted, then the absorbance is defined to be -log 10 T absorbance units. Transmitted through a partially absorbing substance. absorbance unit (AU) a logarithmic unit used to measure optical density, the absorbance of light Magnetic flux density: 1 abtesla = 10 -4 tesla Following are the SI equivalents for each of the "ab" units:Įlectric current: 1 abampere = 10 amperesĮlectric charge: 1 abcoulomb = 10 coulombs Replaced almost completely by the corresponding SI Although these units are defined naturallyĪs part of the CGS system, all of them except the abampere and abcoulomb areĮither much too large or much too small for most applications. These units are also indicated by the notationĮmu (as in "volt emu"). ab- a prefix indicating that an electrical unit is part of the CGSĪbsolute electromagnetic system. A sheet of size A n has a width of 100♲ -1/4- n /2Ĭentimeters and a length of 100♲ 1/4- n /2Ĭentimeters (rounded to the nearest millimeter). Wikipedia has a description of this scale. A a symbol for international standard paper sizes, followed by the size number,Īs in A4 for a standard business-letter sheet. a or A shortened version of am or AM in a statement of time (see below). The symbol is often seen inĬombinations such as Ma (million years) or Ga (billion years). To use the traditional symbol yr for most purposes, scientists use Although English-speaking countries continue Units: A A a an international symbol for year, taken from
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