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


gigajoule (GJ)
a metric unit of energy commonly used in the energy industry. One gigajoule equals 947 817 Btu, 277.7778 kilowatt hours, or about 9.48 therms.

gigaliter (GL or Gl)
a metric unit of volume equal to 109 liters or one million cubic meters. This is equivalent to 810.713 acre feet or 35.315 million cubic feet.

gigameter (Gm)
a metric unit of distance equal to one million kilometers or about 621 371.2 miles. Seldom used, this unit would be a good yardstick for the inner Solar System: the distance from the earth to the sun is about 149.60 gigameters.

gigaparsec (Gpc)
a non-metric unit of distance equal to one billion parsecs, 3.2616 billion light years, or 30.856 78 zettameters (30.856 78 x 1021 kilometers). The unit is used in astronomy.

gigapascal (GPa)
a metric unit of pressure. One gigapascal equals 10 kilobars or approximately 145 038 pounds (72.519 short tons) per square inch. Pressures in this range are common inside the earth and can be produced by various high-energy events.

gigatonne (Gt)
a metric unit of mass or weight equal to one billion metric tons (tonnes) or about 2.2046 trillion pounds. This very large unit is used, for example, in discussing the amounts of carbon added to the atmosphere by human activities.

gigawatt (GW)
a metric unit of power equal to one billion (109) watts or about 1.341 million horsepower.

gigawatt hour (GW•h)
a metric unit of energy equal to one billion watt hours, 3.6 terajoules, or about 3.412 billion Btu.

gigayear (Gyr)
a unit of time equal to one billion years. The international symbol Ga is also used, the 'a' being taken from the Latin word annus for a year.

gillion
an informal alternate name for the number 109, called 'billion' in America but often called 'milliard' in France and 'thousand million' in Britain. The reasoning here is that if mega- means a million and tera- a trillion, then giga- should mean a gillion!

gin
one of several spellings used in English for the jin, the Chinese weight unit also called the catty.

Glasgow coma scale (GCS)
a scale used in emergency medicine to assess the condition of trauma victims and other partially-conscious patients. The scale range is 3-15; patients with Glasgow scores of 3-8 are usually said to be in a coma. The score is obtained by observing the patient's eye-opening, motor response, and response to commands. A table is provided.

glass
another name for the U.S. cup (236.6 milliliters). Doctors in the U.S. are fond of saying that everyone should drink 8 glasses of water a day, and this is the amount they have in mind for a glass.

glass
an informal unit of volume used in Australian pubs. In several states of Australia a glass of beer is usually 200 milliliters, but it is 235 milliliters in Queensland and 285 milliliters in Western Australia.

glean
an old English unit of quantity for herrings, equal to 25 fish.

gm
an incorrect symbol for the gram (see below). The correct symbol is g.

GMT
abbreviation for Greenwich Mean Time, the standard time of longitude 0°. This meridian of longitude, called the prime meridian, was fixed as the longitude of the Royal Greenwich Observatory in London by the International Meridian Conference of 1884. GMT is five hours later than U.S. Eastern Standard Time. The abbreviation UT (Universal Time) h...

gnat's eye
an idiomatic 'unit' of distance; it's common to hear that something is 'as small as a gnat's eye.' In fact, the eyes of typical gnats tend to have diameters similar in size to a hair's breadth: roughly 100-150 micrometers (0.10-0.15 millimeters).

go
a traditional Japanese unit of liquid volume. One go is about 180.39 milliliters, 0.3812 U.S. pint, or 0.3174 British imperial pint.

goad
a traditional unit of distance sometimes used in measuring cloth. One goad is equal to 54 inches or 1.5 yards (1.3716 meters). A goad was originally a spear; later it was a pointed rod used for prodding animals to get a move on. The unit must have originated as the length of such an instrument.

gpf
symbol for gallons per flush, a specification sometimes found on toilets. 1 gpf = 3.785 liters per flush (Lpf). U.S. government regulations now require the use of low-flush toilets of 6.0 Lpf = 1.585 gpf or less.

gpm, gps
customary symbols for gallons per minute (gal/min) and gallons per second (gal/s), traditional units for measuring the flow of liquids. 1 gpm equals about 3.785 41 liters per minute (L/min) if U.S. gallons are meant, or exactly 4.546 09 L/min if British imperial gallons are meant.

gr
an ambiguous symbol, traditionally used in English both for the grain and the gross. It has also been used, very improperly, for the gram (g). In the metric world, gr is often the symbol for the grad or grade (next entry).

grade
a measure of the steepness of a slope, such as the slope of a road or a ramp. Usually stated as a percentage in the U.S, the grade is the same quantity known as the slope in mathematics: the amount of (vertical) change in elevation per unit distance horizontally ('rise over run'). Thus a 5% grade has an elevation gain of 0.05 meter for each meter o...

grade
a measure of quality for ball bearings. A bearing of grade g is required to be spherical to an accuracy of g parts per million (g 10-6). Thus lower grade numbers represent better bearings; a 25 grade bearing is spherical to within 25 ppm, but a 1000 grade bearing is only spherical to within 1000 ppm, or 0.1%.

grade point (gp)
a unit of academic recognition used in U.S. schools and colleges. To compute the number of grade points awarded to a student for a course, the student's grade (often assigned as a letter or a percentage) is converted to a standard scale (traditionally 0.0-4.0, with 4.0 being the highest score). This scale number is multiplied by the number of semes...

grain (gr)
a traditional French unit of weight equal to 53.115 milligrams.

grain per gallon (gr/gal or gpg)
see gpg above.

gram force
see gram weight, below.

gram per square meter (g/m2 or gsm)
a common metric unit of areal density, used for paper, fabric, and similar materials. One gram per square meter is equal to about 0.029 4935 ounce per square yard. The symbol gsm is commonly used for this unit, but g/m2 is the proper SI symbol.

gram rad
a name sometimes used for the rad, a unit of radiation dose.

gran
a traditional German weight unit, varying in size but typically about 60 milligrams.

grand
slang for 1000, especially the sum of 1000 dollars in the U.S. or 1000 pounds in Britain.

grav (g)
another name for the unit of acceleration usually called the g (see above).

great hundred
a traditional unit of quantity equal to 120 instead of 100. The great hundred equals 6 score or 2 shocks. Merchants in medieval England used both the great hundred and the gross (144) in specifying quantities, but more recently the gross has been much more common.

great year
the Platonic year.

Gregorian year
a unit of time equal to exactly 365.2425 days, the average length of a year in the Gregorian calendar currently used throughout the world. See year .

grit
a measure of fineness for abrasive materials such as sandpaper, sanding belts, or the finer materials used to polish optical surfaces. Originally the grit number was the number of holes in a standard screen; if the screen had, say, 240 holes, then the particles that would pass through the screen were described as 240 grit. However, very fine abrasi...

gros
a traditional French weight unit equal to 3 deniers (about 3.824 grams).

gross ton (GT)
the name 'gross ton' is used in at least two ways: (1) as another name for the British Imperial or long ton of 2240 pounds (see ton ), and (2) as another name for the register ton, a unit of volume equal to 100 cubic feet (see ton ), in describing the entire interior volume of a ship as opposed to the cargo-carrying capacity. ...

gsm
a common but non-standard symbol for grams per square meter (g/m2), the metric unit of density for paper and for fabric. Paper density measured in this unit is often called grammage.

Gunter's chain
the traditional surveyor's chain equal to 4 rods; see chain.

gutenberg
a unit of distance used in typography, equal to 1/7200 inch or 3.5278 micrometers. The gutenberg is 0.01 point , more or less, depending on how the point is defined. The unit is named for Johannes Gutenberg (ca. 1390-1468), the German inventor of printing from movable type.

hacienda
a large traditional unit of land area in Mexico and the southwestern U.S. The word also refers to a large estate, ranch, or plantation. As a unit, it equals 5 square leguas or 125 million square varas. Using the Texas definition of the vara, this would be about 8960 hectares or 22 140 acres (34.59 square miles). Using the shorter Mexican vara, it w...

halakim (hl)
plural of helek (see below). The word is also transliterated as chalakim or chlakim.

half
a unit of proportion equal to 1/2. The English word 'half,' like the German prefix 'halb-,' is often placed before the name of a unit to create a combination which functions as a new unit equal to half the old one. Half dozen, half hour, and half gallon are typical and common examples.

hartree (Eh)
a unit of energy used in atomic and moleclar physics, equal to about 4.3598 x 10-18 joule or 27.212 electron volts. The unit is named for the British physicist and mathematician Douglas R. Hartree (1897-1958).

hat trick
an informal unit of quantity equal to 3. The unit is used in sports in counting goals, especially goals scored by the same player. It originated in cricket but is more familiar to North Americans in ice hockey. No one seems to know for sure why 3 goals came to be called a hat trick. According to one popular account, cricket clubs in England sometim...

head (hd)
a notation seen in measurements of water pressure; see foot of head.

heaped bushel
a traditional unit of volume in the United States, the heaped bushel is just what its name implies: the volume of a bushel container filled to overflowing. Officially, the heaped bushel was supposed to equal 1.278 regular, or 'struck' bushels; this is a volume of 2748.237 cubic inches, 1.5904 cubic feet, or 45.036 liters. In practice, the heaped bu...

heat index (HI or HX)
a measure of the combined effect of heat and humidity on the human body. U.S. meteorologists compute the index from the temperature T (in °F) and the relative humidity H (as a fraction; that is, H = 0.65 if the relative humidity is 65%). The formula used is HI = -42.379 + 2.04901523 T + 1014.333127 H - 22.475541 TH - .00683783 T2<...

heating degree day (HDD)
see degree day.

hebdo-
an obsolete metric prefix denoting ten million (107). It was coined from the Greek hebdomos, seventh. A group of seven is sometimes called a hebdomad, a word related to the French hebdomadaire, weekly.

hectogram (hg)
a common metric unit of mass, equal to 100 grams or about 3.5274 ounces.

hectoliter (hL or hl)
a common metric unit of volume. The hectoliter equals 100 liters, 0.1 cubic meter, 26.417 U.S. liquid gallons, 21.999 British imperial gallons, or 3.5315 cubic feet.

hectometer (hm)
a metric unit of distance equal to 100 meters, 328.084 feet, or 109.361 yards. This unit isn't used much in everyday life in metric countries, but it appears in various scientific contexts.

hectopascal (hPa)
a metric unit of pressure equal to 100 pascals or 0.1 kilopascal (kPa). The hectopascal, used almost entirely in measurements of air pressure, is identical to the millibar (mb). The millibar has been used to measure air pressure for many years, but it is not an SI unit. Although meteorologists in various countries use the hectopascal as a kind of a...

heer
a traditional measure of length for linen and woolen yarn, equal to 2 cuts or 1/6 hank (see above). This is equivalent to 80 yards (73.152 meters).

helek (hl)
a traditional Hebrew unit of time equal to 1/1080 hour, 1/18 minute or 10/3 seconds. The plural is halakim. Halakim are used in formulas establishing the instant of new moon, which marks the start of the month in the Jewish calendar. In English, the unit is often called a part of an hour. The Jews inherited this unit from the Babylonians; it was wi...

hemidemisemiquaver
the shortest named unit of relative time in music, equal to 1/8 quaver, 1/64 whole note or 1/128 breve.

hemina
a Roman unit of liquid volume, equal to 1/2 sextarius or about 265.6 milliliters (0.561 U.S. pint or 0.467 British Imperial pint).

hemisphere
a traditional unit of solid angle equal to 1/2 sphere, 2pi steradians, or about 20 626.48 square degrees.

heptad
a unit of quantity equal to 7.

hexad
a unit of quantity equal to 6.

hexit
a unit of information equal to 4 bits or 1/2 byte. A string of 4 bits has 16 possible states (0-15) and is usually represented as a single base-16, or hexadecimal, digit (in the hexadecimal system the letters A through F are used to represent the numbers 10 through 15, respectively). A hexit of data is also known as a nibble or a quadbit.

homestead
a historic unit of area in the United States, equal to 160 acres (64.75 hectares). Under the Homestead Act passed by Congress in 1862, settlers in the western states were allowed to take title to a homestead of 160 acres of land by registering a claim, settling on the land, and cultivating it. A homestead equals 1/4 square mile, or 1/4 section in U...

hoppus ton (HT)
a traditional unit of volume in British forestry. One hoppus ton is equal to 50 hoppus feet or 1.8027 cubic meters. Shipments of tropical hardwoods from Southeast Asia, especially shipments of teak from Myanmar (Burma), are still stated in hoppus tons.

horse
slang for the horsepower, as in '200-horse engine.'

horsepower hour (hp hr)
a unit of work or energy equal to the work done at the rate of 1 horsepower for 1 hour. The horsepower hour equals 1 980 000 foot pounds or approximately 2.685 megajoules, 2545 Btu, 641.1 (large) Calories, or 745.7 watt hours.

house
in astrology, each sign of the Zodiac is called a house; thus the house can be considered a unit of angle measure equal to 1/12 circle or 30°.

hu
a traditional Chinese unit of liquid volume. The hu contains about 51.77 liters, 13.676 U.S. gallons, or 11.389 British imperial gallons.

hubble
a unit of distance sometimes used in astronomy. The hubble is a gigantic unit, equal to 109 light years. This is 9.4605 x 1021 kilometers (9.4605 yottameters, if you please), 5.8785 sextillion miles (U.S.), 63.240 x 1012 astronomical units, or 306.595 megaparsecs. In practice, mos...

hue
a numerical measure of color; see color units.

hundred
a unit of quantity. In commercial use in old England the term 'hundred', or cent (C), did not always mean an even 100; sometimes it meant 120 (the 'great hundred') or some other number, depending on the item. For fish, the exact number in a hundred varied with the species.

hundred
an old English unit of area equal to 100 hides (see above). This is roughly 12 000 acres, 5000 hectares, or 18.75 square miles. The hundred is approximately the area of a village with its associated fields, so the name 'hundred' came to mean a minor division of a shire or county. This use carried over to the American colonies, where, for example, m...

hyl
an obsolete MKS unit of mass. One hyl is the mass that is accelerated at one meter per second per second by one kilogram of force (kgf). Since 1 kgf = 9.806 65 newtons, the hyl is equivalent to 9.806 65 kilograms. The name of the unit comes from an ancient Greek word for matter.

icfm
abbreviation for inlet cubic feet per minute, a unit traditionally used to measure the capacity of air compressors.

IGPM
abbreviation for imperial gallons per minute.

immi
a traditional Swiss unit of liquid volume. The immi has been brought into the metric system and now equals exactly 1.5 liters (about 3.17 U.S. liquid pints).

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

Imperial gallon (gal or IG)
a traditional unit of volume equal to about 1.201 U.S. liquid gallon or 4.546 liters. See gallon . In Canada, the term 'Imperial' is used frequently to distinguish the British Imperial units from the corresponding U.S. units.

Imperial units
the units of the British Imperial system, adopted by Parliament in 1828. The basic units of the system are the foot, the avoirdupois pound, and the Imperial pint. The Weights and Measures Acts of 1963 and 1985 have redefined the Imperial units in term of the SI units.

inch of water gauge (in wg or "wg)
another common name for the inch of water column. The word 'gauge' (or 'gage') after a pressure reading indicates that the pressure stated is actually the difference between the absolute, or total, pressure and the air pressure at the time of the reading.

inch pound (in•lbf or in lb)
a traditional unit of work or energy, equal to 1/12 foot pound, about 0.112 985 joule or 1.0709 x 10-4 Btu.

in d.
abbreviation for the Latin in die, daily, a unit of frequency used in medical prescriptions.

international foot
the current foot unit of the English-speaking countries, equal to exactly 30.48 centimeters. See survey foot for additional information.

international nautical mile
the nautical mile as currently defined by international agreement, equal to exactly 1852 meters or 6076.11549 feet. This long name is sometimes used to distinguish the current nautical mile from older units.

Internet time
a global decimal time system proposed by the Swatch Corporation. See beat for more information.

ips
an abbreviation for inches per second (in/s), a traditional unit of velocity equal to 2.54 centimeters per second.

ipy
an abbreviation for inches per year (in/yr), a traditional unit for corrosion rates.

Irish mile
the traditional mile in Ireland is 6720 feet, which is 1.272 727 English mile or 2.048 256 kilometers. The discrepancy arose because the Irish perch, or rod, was standardized at 21 feet instead of the English figure of 16.5 feet. Just as in England, the Irish chain was equal to 4 perches (84 feet instead of 66 feet), the Irish furlong was equal to ...

ISO
the 'short name' of the International Organization for Standardization. Based in Switzerland, the ISO sets international industrial standards, including standards for the use of units of measurements. For ISO film ratings, see ASA.

IT calorie
common name for the international steam table calorie, a unit of energy equal to exactly 4.1868 joules. See calorie.

jag
a traditional British name for a small load, especially a small load of hay. Never standardized, the jag represented roughly 20-25 bushels (0.7-1.0 cubic meters).

jar
a traditional unit of electric capacitance, approximately equal to the capacitance of one of the Leiden jars used in electrical experiments as long ago as the eighteenth century. Benjamin Franklin is said to have measured the storage power of his electrical equipment in jars. There are 9 x 108 jars in a farad, so 1 jar is app...

jeroboam
a large wine bottle holding about 3 liters, 4 times the volume of a regular bottle. A jeroboam is sometimes called a double magnum.

jersey foot
a traditional unit of distance in Jersey, one of the Channel Islands. Also called the pied-perche, the jersey foot is equal to 11 English inches or 0.9167 English foot. The jersey foot is divided into 12 jersey inches, making 13.09 jersey inches to an English foot.

jiffy
a unit of time used in chemistry and physics, equal to a 'light centimeter,' that is, the time required for light to travel a distance of one centimeter. This is a very brief interval indeed, about 33.3564 picoseconds. This definition of the jiffy was proposed by the American physical chemist Gilbert N. Lewis (1875-1946), who was one of the first t...

jigger
a unit of volume for liquor, usually considered equal to 1.5 (U.S.) fluid ounces or 44.360 milliliters.

jitro
a traditional unit of land area in the Czech Republic, identical to the Austrian joch (see below).