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 HowMany - Unit Dictionar
Category: Mathematics and statistics > Dictionary of unit measurements
Date & country: 26/09/2008, USA
Words: 1293


lumberg
an older name for the talbot, the unit of luminous (light) energy equal to 1 lumen second.

lumen hour (lm h)
a unit of quantity of light, equal to one lumen of light flux continued for one hour. The lumen second (lm s) is defined similarly.

lunar day
another name for the tidal day, a unit of time equal to 24 hours 50 minutes used in tidal predictions.

lunar month, lunation
names for the interval between two successive new moons, a unit of time equal to 29.530 59 days. See month .

luster, lustre, lustrum
a traditional unit of time equal to 5 years. In ancient Rome the Lustrum was a ceremony of expiation and purification for the whole population of the city, carried out every 5 years after the completion of the census. The use of luster or lustrum as a unit of time in English was fairly common in well-educated circles as long as 'well-educated' mean...

Ma
a symbol for one million years, often used in astronomy and geology. The 'a' stands for the Latin annum.

mab
symbol for 'meters above bottom' (bottom of the sea), a unit used in oceanography.

mace
a traditional Chinese unit for weighing precious metals, especially silver. In the European colonial period, the mace was considered equal to 0.1 tael or liang; this would be 2/15 ounce or about 3.78 grams.

maf or Maf
a symbol for one million acre feet. This symbol, commonly used in reservoir management in the U.S., should be written Maf. 1 Maf = about 1.2335 billion (109) cubic meters.

magnum
a traditional unit of volume for wine, generally equal to 2 bottles. This is now exactly 1.5 liters (about 2.114 U.S. quarts).

mahnd
a traditional Arab weight unit equal to about 2.04 pounds or 925 grams.

mandel
a traditional German unit of quantity equal to 15.

man hour
a common unit of labor equal to the work of one person for one hour. The less restrictive term person hour is gradually coming into use.

manpower
an informal unit of power equal to 0.1 horsepower or about 74.57 watts. The unit seems to have been invented by American engineers.

marathon
a traditional unit of distance used in athletics. The length of a marathon is exactly 42 195 meters (about half an inch longer than 26 miles 385 yards). Invented for the first modern Olympic Games at Athens in 1896, the marathon recalls a run made in 490 BC by a Greek soldier (possibly Pheidippides) to bring to Athens the news of the Greek victory ...

marc, marco, or mark
traditional units of weight in various countries of Western Europe. In each country the unit equals 1/2 the unit corresponding to the English pound. Thus the French marc equals 1/2 livre, 8 onces or about 244.75 grams; the Spanish marco equals 1/2 libra or about 230 grams; the German mark equals 1/2 pfund or about 280.5 grams; and the English mark ...

marine league
an informal name for the league as used at sea: a unit of distance generally equal to 3 nautical miles (5556 meters).

mark twain
see twain.

masl
a common symbol for 'meters above sea level' used in geology and geography.

mAU
a symbol for the milli-absorbance unit. An increase in absorbance of 1 mAU corresponds to a reduction in transmittance of about 0.2305%.

MBF or MBM
traditional symbols for 1000 (not one million) board feet, a unit of volume for timber equal to 250/3 = 83.333 cubic feet or 2.360 cubic meters. 'BM' stands for 'board measure.'

mbsl
a common symbol for 'meters below sea level' used in geology and oceanography.

MBH, MBtuh
symbols for 1000 (not one million) Btu (British thermal units) per hour, a unit traditionally used in the U.S. heating and air conditioning industry to state rates of heating or cooling. One MBH equals about 0.293 071 kilowatt.

mc- or mc
alternate symbol for micro- (see below). This prefix is often seen in the symbol mcg for the microgram. The use of the symbol mc- for micro- became established because typewriters and early dot matrix printers did not have the proper symbol µ-. Also, many hospitals require the use of mc- in all handwritten notes and records, because a hastily...

mc
Italian abbreviation for the cubic meter (metro cubico). This is a non-standard symbol; the proper symbol is m3.

MCF
a traditional symbol for 1000 (not one million) cubic feet, a unit of volume equal to about 28.317 cubic meters.

Mcfd
a symbol for 1000 cubic feet per day, a unit of water flow used by many U.S. water supply companies and agencies. 1 Mcfd = 19.665 liters (5.195 U.S. gallons) per minute.

Mcfe
a symbol used in the natural gas industry for 1000 (not one million) cubic feet of gas equivalent (cfe). This is really an energy unit equal to about 1.091 gigajoules (GJ).

mcg, mcL
common but undesirable symbols for the microgram and microliter, respectively. Entries for those units appear below.

MCM
a symbol for 1000 circular mils, a unit of area equal to about 0.5067 square millimeter commonly used in stating wire gauges. This symbol is being replaced by the less-confusing symbol kcmil.

mease
a unit of quantity formerly used by fishermen. The mease equals the number of herring in a basket, roughly 620.

measurement ton (MTON or MT)
a unit of volume used for measuring the cargo of a ship, truck, train, or other freight carrier, equal to exactly 40 cubic feet, or approximately 1.1326 cubic meters. This unit was traditionally called a freight ton (see ton ), but that term now means a metric ton of freight in most international usage. However, the confusion seems impos...

mebi- (Mi-)
a binary prefix meaning 220 = 1 048 576. This prefix, adopted by the International Electrotechnical Commission in 1998, is intended to replace mega- for binary applications in computer science. (This replacement does not seem to be happening.) The prefix is a contraction of 'megabinary.'

MED
a common symbol for 'minimum erythemal dose,' the smallest amount of ultraviolet radiation that produces observable reddening (erythema) of the skin. (Skin is sensitive to reddening by radiation in only a narrow band of wavelengths around 300 nanometers.) The MED obviously varies from one person to another. Doctors and tanning salon operators typic...

megabar (Mbar)
a metric unit of pressure. The megabar equals one million bars, 100 gigapascals (GPa) or about 14.503 million pounds per square inch. Such intense pressures are found inside the earth or in various advanced scientific experiments.

megabarrel (Mbbl, Mbo, MMb, or Mb)
a unit of volume used in the energy industry, equal to one million barrels of oil. One megabarrel equals 42 million U. S. gallons, which is about 158.987 megaliters (ML).

megabase (Mb)
a unit of genetic information equal to the information carried by 1 million pairs of the base units in the double-helix of DNA; also used as a unit of relative distance equal to the length of a strand of DNA containing 1 million base pairs. In humans, one megabase corresponds approximately to a gene separation of one centimorgan.

megabecquerel (MBq)
a unit of radioactivity equal to one million atomic disintegrations per second or 27.027 microcuries.

megabyte (MB)
this unit of information is very common in the computer world, but it is poorly defined. Often it means 1 000 000 bytes, but sometimes it means 220 = 1 048 576 bytes. As if that weren't confusing enough, the 1.44 megabytes stored on 'high density' floppy disks are actually megabytes of 1 024 000 bytes each. This uncertainty i...

megacycle (Mc)
1 million cycles, a term sometimes used as an informal name for the megahertz.

megadalton (MDa)
a unit of mass equal to one million atomic mass units. See dalton.

megaflops (Mflops)
a unit of computing power equal to one million floating point operations per second. See flops.

megagram (Mg)
an SI unit of mass equal to one million grams or 1000 kg. This means the megagram is identical to the tonne (metric ton). Large masses are almost always stated in tonnes in commercial applications, but megagrams are often used in scientific contexts. One megagram equals about 2204.623 pounds.

megahertz (MHz)
a common unit of frequency equal to one million per second. Frequencies of radio waves are commonly stated in megahertz.

megajoule (MJ)
a common metric unit of work or energy. The megajoule equals one million joules, which is approximately 737 562 foot pounds, 947.8170 Btu, 238.846 (kilogram) Calories, or 0.277 778 kilowatt hours.

megakelvin (MK)
a unit of temperature equal to one million kelvins. This unit is used in astrophysics; temperatures in megakelvins are found in the interiors of stars or in highly excited plasmas. The reciprocal megakelvin (MK-1) is used in colorimetry.

megalerg
a CGS unit of energy equal to 106 ergs or 0.1 joule (0.073 756 foot pound). The 'l' was added to 'mega-erg' to make the unit pronounceable.

megaline
a metric unit of magnetic flux, equal to one million lines or 0.01 weber.

megaliter (Ml or ML)
a metric unit of volume equal to 1000 cubic meters. Commonly used in reservoir and water system management outside the U.S., the megaliter equals 264 172 U.S. gallons or 0.810 713 acre foot.

megalithic yard
a unit of distance equal to about 83 centimeters or 2.72 feet, defined in 1951 by the Scottish engineer Alexander Thom (1894-1985). Thom claimed this unit was used in the construction of many megalithic monuments, including Stonehenge. If so, the unit was probably measured by the length of a workman's arm.

megameter (Mm)
a metric unit of distance equal to 1000 kilometers or about 621.371 miles. Although this appears to be an appropriate unit for longer distances on the earth, the megameter is seldom used.

megampere (MA)
a unit of electric current equal to one million amperes. This unit is used in plasma physics and fusion research.

meganewton (MN)
a metric unit of force equal to one million newtons. One meganewton equals about 101 972 kilograms of force or 224 809 pounds of force. The main engines of the U.S. space shuttle have a maximum thrust of about 2.28 meganewtons.

megaohm (megohm)
a common unit of electric resistance equal to one million ohms. The spelling megohm is also used.

megaparsec (Mpc)
the longest distance unit in common use, the megaparsec is used by astronomers studying the most distant quasars and galaxies. One megaparsec equals one million parsecs, 3.2616 million light years or 30.857 x 1018 kilometers (30.857 zettameters).

megapascal (MPa, MP)
a common metric unit of pressure or stress equal to one million pascals or one newton per square millimeter. One megapascal equals 10 bars or approximately 145.038 pounds per square inch (lbf/in2 or psi) or 20 885.5 pounds (10.443 U.S. tons) per square foot. The symbol MP is used fairly commonly in engineering, but it is not ...

megapixel
a unit used to describe the size or resolution of an image or of a digital camera. One megapixel is one million pixels (picture elements, or 'dots'). For example, a rectangular image 1000 pixels by 1000 pixels is comprised of one megapixel.

megapond (Mp)
a metric unit of force equal to 1000 kilograms of force (kgf). The megapond also equals 9806.65 newtons, or 2204.6226 pounds of force in the traditional English system. Although it is considered obsolete, the megapond is still used sometimes by engineers in Europe, especially in Germany.

megatonne (Mt)
a metric unit of mass or weight equal to one million metric tons (tonnes), one teragram (Tg), or about 2.2046 billion pounds.

megawatt (MW)
a common metric unit of power. One megawatt is equal to one million watts, about 1341.02 horsepower, or 947.817 Btu per second.

megawatt day (MW•d or MWD)
a unit of energy used in the nuclear power and nuclear weapons industries. One megawatt day equals exactly 24 megawatt hours, 86.4 gigajoules (GJ), about 81.89 million Btu, or about 63.7 billion foot pounds.

megayear (Myr or Ma)
a unit of time equal to one million years.

megohm
a common unit of electric resistance equal to one million ohms. This simplified spelling of megaohm is approved by the Institute of Electrical and Electronics Engineers (IEEE).

melchior
a huge bottle of champagne, holding about 18 liters.

Mercalli intensity scale
an empirical scale for rating the effects of an earthquake, as opposed to its strength (see magnitude above). Mercalli estimates are stated as Roman numerals (I-XII) to avoid confusion with magnitude estimates on the Richter scale. The scale is named for the Italian geologist Giuseppe Mercalli (1850-1914), who devised the first version ...

mercantile pound (lb merc)
a historic English unit of weight, the mercantile pound (libra mercatoria) was the commercial predecessor of the avoirdupois pound . Used from about 1100 to 1300, the mercantile pound contained 15 troy ounces or 7200 grains. This is equivalent to about 1.0286 avoirdupois pounds or 466.55 grams.

mesh
a traditional unit used to measure the fineness of woven products such as fishing nets, fencing fabric, window screening, etc., equal to the number of strands per inch. For n mesh fabric, the distance between strands is 1/n inch or 25.4/n millimeter.

met
a unit of metabolism. Metabolism, the sum of all the processes going on in the body to sustain life, is measured in units of power expended per unit of body surface area. One met is the metabolism of a seated, resting person, equal to about 58.15 watts per square meter (W/m2) or 13.89 calories per second per square meter (cal...

meter-atmosphere
another name for the atmo-meter.

meterlambert or meter-lambert
another name for the nit, an MKS unit of luminance equal to one candela per square meter. The name is coined by analogy with the footlambert.

methuselah
a large wine bottle holding about 6 liters, 8 times the volume of a regular bottle.

metric carat
the current internationally-recognized carat, equal to exactly 200 milligrams.

metric grain
a unit of mass sometimes used by jewelers, equal to 50 milligrams or 1/4 carat. This unit is often used for pearls and is sometimes called the pearl grain.

metric hundredweight
an informal unit of mass equal to 50 kilograms or approximately 110.231 pounds, close to the traditional British hundredweight of 112 pounds. This unit is also known by its German name, the zentner, or (in English) the centner.

metric pound
an informal name for a mass of 500 grams (0.5 kilogram or 1.1023 pound).

metric quintal
a unit of mass equal to 1 decitonne, 100 kilograms or about 220.462 pounds. See quintal for a more complete description.

metric slug
see TME.

metric ton unit (mtu)
a unit of mass used in mining to measure the mass of the valuable metal in an ore. Customarily, the metric ton unit is defined to be one metric ton of ore containing 1% metal, but it is the metal, not the ore, that is being measured. Thus the unit is really a unit of mass equal to 10 kilograms (22.0462 pounds).

MeV
the symbol for one million electronvolts. Thanks to Einstein's equation E = mc2 equating mass wth energy, the MeV can be regarded either as a unit of energy equal to 160.217 646 2 femtojoules, or as a unit of mass equal to 1.782 662 x 10-27 gram or 0.001 073 544 atomic mass unit. This is 1.956 951 times...

MFD, mfd
common but incorrect symbols for the microfarad (see below). The correct symbol is µF, or mcF if µ is not available.

mg-at
an obsolete symbol for 'milligram atom', an equally obsolete name for the millimole (mmol).

mg/dl
symbol for milligram per deciliter, a unit used in U.S. medicine to measure the concentration of cholesterol and other substances in the blood. 1 mg/dl equals 0.01 grams per liter (g/L). Internationally, the SI unit for data of this type is millimoles per liter (mmol/L); see the table of SI Units for Clinical Data for conversions of many common mea...

mg-eq
an obsolete symbol for 'milligram equivalent', an equally obsolete name for the milliequivalent (mEq).

mg/kg
symbol for milligram per kilogram, a unit used in medicine to measure dosage rates. 1 mg/kg is equivalent to 10-6 g/g or 1 part per million based on the patient's body weight.

mic
an informal name for the microgram, pronounced 'mike.'

mickey
a unit used in computer science in programming mice and similar input devices. One mickey is the length of the smallest detectable movement of the mouse. This depends on the equipment. Typical values are in the range 1/200 to 1/300 inch or roughly 0.1 millimeter. Obviously, the name comes from the Disney cartoon character Mickey Mouse.

microarcsecond (µas)
a unit of angle measurement sometimes used in astronomy. The microarcsecond equals 10-6 arcsecond or about 4.8481 picoradian.

microcurie (µCi)
a common unit of radioactivity. The microcurie equals 10-6 curie or 37 kilobecquerels; this corresponds to a radioactivity of 37 000 atomic disintegrations per second.

microdegree (µdeg)
a unit of angle measure equal to a millionth of a degree or exactly 36 milliarcseconds.

microequivalent (µEq or µeq)
a unit of relative amount of substance equal to 10-6 equivalent weight. This unit is used, for example, in stating the concentrations of ions in drinking water.

microgray (µGy)
a unit of radiation dose equal to a millionth of a gray or 0.1 millirad. Small doses of this size are often provided by natural sources in the environment.

micronewton (µN)
a unit of force equal to a millionth of a newton or 0.1 dyne. The unit is often used in astronautical engineering to describe the tiny forces applied to spacecraft to adjust their attitudes in space.

micropoise (µP, µPo, or µPs)
a unit of dynamic viscosity used primarily for describing the viscosities of gases. One micropoise equals 10-6 poise or 10-7 pascal second (Pa•s).

microsecond (µs or µsec)
a unit of time equal to a millionth of a second.

microstrain (µstrain)
a common engineering unit measuring strain. An object under strain is typically deformed (extended or compressed), and the strain is measured by the amount of this deformation relative to the same object in an undeformed state. One microstrain is the strain producing a deformation of one part per million (10-6).

microtesla (µT or mcT)
a common unit of magnetic field intensity equal to 10-6 tesla. The unit is widely used to measure the strength of electromagnetic fields generated by powerlines or electronic equipment. By comparison, the strength of the Earth's own magnetic field at the surface is about 50 microteslas. One microtesla equals 0.01 gauss.

middy
an informal unit of volume for beer used in many Australian pubs. A middy is generally 285 milliliters (or 10 British fluid ounces), larger than a pony but smaller than a schooner.

miglio
the traditional Italian mile. The miglio equals 1628 yards, which is 0.925 English mile or about 1488.6 meters. This is 32 yards (29.3 meters) shorter than the classical Roman mile.

miil or mijl
alternate spellings for the Scandinavian mil (see below).

mil
a common slang name for the milliliter (mL) or the millimeter (mm).