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

pin
a traditional British unit of volume, used for beer. A pin is very different from a pint: it is equal to 1/8 barrel or 4.5 imperial gallons (20.457 liters). There are 2 pins in a firkin. See also polypin (below).

pint (pt)
a traditional unit of volume in Scotland equal to 2 choppins or 4 mutchkins. The Scots pint varied with time and locality, but it was eventually standardized as the volume of the Stirling jug, a vessel holding about 104.2 cubic inches or 1.708 liters. This is almost exactly 3 Imperial pints or 3.6 U.S. liquid pints.

pint (pt)
a unit of volume used in South Australian pubs. A pint of beer is generally 425 milliliters in South Australia, or roughly 3/4 imperial pint (15 fluid ounces). In Queensland a pint glass typically holds 560 milliliters, very nearly an Imperial pint.

pitch
another name for 'characters per inch,' a unit used in printing.

pixel
a picture element. Pixels do not have a fixed size; their diameters are generally measured in micrometers (microns). Although the pixel is not a unit of measurement itself, pixels are often used to measure the resolution (or sharpness) of images. As a hypothetical example, a 600 x 1000 pixel image has 4 times the pixel density and is thus 4 times s...

planck
an MKS unit of 'action' (energy expended over time) or of angular momentum. The planck is equal to 1 joule second (J•s) or about 0.7375 foot pound second (ft•lb•s). The unit honors the German physicist Max Planck (1858-1947), the originator of quantum theory.

Platonic year
a unit of time used in astronomy. The earth's axis of rotation is not fixed in space; the attraction of the moon causes it to slowly trace out a circle in the sky. This motion, called precession, changes the orientation of the sky as seen from the earth's surface: the poles appear to shift their locations and the sun's point of crossing the equator...

plf
symbol for pounds per linear foot (lbm/ft), a common unit of load in engineering. 1 plf = 1.488 164 kilograms per meter (kg/m). The symbol is also used sometimes for pounds of force per linear foot (lbf/ft), in which case 1 plf = 14.593 90 newtons per meter (N/m).

plf
a common abbreviation for 'per linear foot.' In this use, 1 plf = 3.280 840 per meter (/m).

pli
a common abbreviation for pounds per linear inch. For load, 1 pli = 17.857 97 kg/m. For pounds of force per linear inch, 1 pli = 175.1268 N/m.

plotter unit
a unit of distance used in typography equal to 1/40 millimeter or 25 micrometers. This, the smallest distance addressed by Hewlett Packard plotters, has become a fairly familiar term in digital graphics design.

PM or pm
abbreviation for the Latin post meridiem, 'after noon,' used after a time to indicate that the time occurs after 12:00 noon. Thus 4:30 pm is the same as 16:30. The notations 'AM' and 'PM' are used extensively in English speaking countries and especially in the United States, where time is usually not stated on a 24-hour basis.

PMPO
abbreviation for 'peak music power output,' which is often claimed by electronics manufacturers as a unit measuring the effective power output of amplifiers, stereo systems, etc. Buyer beware! There is no industry standard for this 'unit,' so it is impossible to determine just what it means.

PN
a symbol for 'nominal pressure,' a measure used for rating piping, valves, fittings, etc. Nominal pressure is essentially the pressure rating of the piping system, measured in bars at a temperature of 20 °C (68 °F). (One bar equals 100 kilopascals or approximately 14.5038 pounds per square inch in traditional English units.) Industrial st...

point (pt)
another name for a mil , a unit of distance equal to 0.001 inch. Points are used with this meaning to measure the thickness, or caliper, of paper or card stock in the paper industry. One point equals 25.4 micrometers or microns.

point (pt)
a measure of the specific gravity of a liquid, typically used in brewing and winemaking. Specific gravity is the mass of a sample of the liquid divided by the mass of an equal volume of pure water. It is a dimensionless (unit-less) number, typically a little larger than 1. Each 'point' represents an increase of 0.001 above 1. For example, a liquid ...

point
a medieval unit of time equal to 1/5 hour, or 12 minutes. The point was divided into 8 moments.

pol
an empirical unit of indoor air pollution introduced by the Danish environmental scientist P.O. Fanger in 1988. One olf is defined as the air pollution produced by one 'standard person', and one decipol is the perceived air pollution level in a space having a pollution source of strength one olf and ventilation with unpolluted air at the rate of 1 ...

pole
see unit magnetic pole.

polegada
the Portuguese 'inch' unit, equal to 1/12 pé, 2.777 centimeters, or 1.093 inches.

pollex (poll)
the Latin word for 'thumb,' sometimes used to mean the inch in botanical descriptions.

poncelet (p)
a unit of power formerly used in France but now obsolete. The poncelet is defined to be the power required to raise a mass of 100 kilograms at a velocity of 1 meter per second. This is equivalent to 980.665 watts or exactly 4/3 metric horsepower (1.315 traditional horsepower). The unit was named for the French mathematician and engineer Jean-Victor...

pond
the Dutch pound, historically about 494 grams (1.089 English pounds). This unit was also used in the former Dutch Indies (now Indonesia) and throughout Southeast Asia. In the Netherlands, the pond has been reinterpreted now as a metric unit equal to exactly 500 grams (1.1023 pounds), like the German pfund.

pond (p)
a metric unit of force, formerly more common and still used for some purposes. A pond is the gravitational force on a mass of one gram; thus it is equal to 980.665 dynes or 0.002 204 622 6 pounds of force. The kilopond was used more often than the pond. The name of the unit is from the Latin pondus, weight.

pony
a small glass for liquor. In the U.S., a pony generally holds exactly 1 (U.S.) fluid ounce or about 29.6 milliliters. The word 'pony' means a small horse, hence anything smaller than normal--in this case, a smaller shot glass.

pony
a small glass for beer. In New South Wales, Victoria, South Australia, and Western Australia, a pony of beer holds 140 milliliters (about 5 British fluid ounces).

pood
see pud.

porosity
in the paper industry, 'porosity' is generally measured by the time (in seconds) required for 100 cubic centimeters of air to pass through one square inch of the paper at a standard pressure difference. Thus the porosity unit is square inch seconds per deciliter (s•in²/dl). This is sometimes called a Gurley unit after th...

pot
a unit of volume used in Australian pubs. A pot of beer is 285 milliliters in Queensland and Victoria, 575 milliliters in Western Australia.

pottle
a traditional unit of volume equal to 1/2 gallon. The unit's name is from the French potel, a type of bottle.

poumar
an acronym for one pound per million yards, a unit of yarn density formerly used in the U.S. textile industry. One poumar equals about 0.496 055 tex.

pound (lb)
a traditional unit measuring the weight of paper; see pound weight, below.

pound mass (lbm)
see pound , above.

pound mole (lbmol)
a unit of amount of substance. One pound mole of a chemical compound is the same number of pounds as the molecular weight of a molecule of that compound measured in atomic mass units. Thus the pound mole is equal to exactly 453.592 37 moles.

power (x)
a term indicating that a measurement is a multiple of some standard quantity. For example, in computer technology, a 16x CD-ROM drive spins a disk 16 times faster than a 'standard' speed drive.

pp
a traditional abbreviation for 'pages.'

ppb, ppm, ppq, ppt, pptr
abbreviations for units of proportion: ppb = part per billion (10^-9), ppm = part per million (10^-6), ppq = part per quadrillion (10^-15), and ppt = part per trillion (10^-12), respectively. However, the abbreviation 'ppt' is also used sometimes for part per th...

ppcm, ppi
abbreviations for pixels per centimeter and pixels per inch, respectively. A pixel is a single 'picture element', so these units measure the resolution, or fineness, of an image.

ppi
abbreviation for pages per inch, a measure of paper thickness.

ppi
abbreviation for pores per inch, a measure of porosity for polyurethane foams and other industrial foam and filter products.

printer's ream
a unit of quantity for paper. An ordinary ream is 480 or 500 sheets; a printer's ream is 516 sheets. The additional amount is to allow for sheets that may be spoiled in shipment. The unit is also called the perfect ream.

prism diopter (PD)
a unit used in optics to measure the deflection of light by a prism. One prism diopter represents a deflection of 1 centimeter measured at a distance of 1 meter from the prism. Mathematically, the deflection in prism diopters is equal to 100 times the tangent of the angle through which the path of the light is bent in passing through the prism.

PRU
abbreviation for the peripheral resistance unit, used in physiology and medicine to assess blood flow in the capillaries. A measurement in PRU's is equal to the blood pressure in millimeters of mercury divided by the flow rate in milliliters per minute. That is, 1 PRU equals 1 mmHg•min/mL = 133.3 Pa•min/mL (or, in proper SI units, almost ...

ps
see pferdestärke above.

psi, psia, psid, psig
traditional symbols for pressure units used in hydraulics and plumbing. psi is a symbol for pound per square inch (see above). psig is a symbol for pound per square inch gauge; this means that the pressure has been read from a gauge which actually measures the difference between the pressure of the fluid and the pressure of the atmosphere. psia mea...

pu
A unit of distance used during the colonial era in China. The pu equals 5 ch'ih, 5.875 feet, or 1.7907 meters.

pud or pood
a traditional unit of weight in Russia. The pud equals 40 funte or 1/30 packen; this is about 16.381 kilograms or 36.11 pounds. The plural is pudi.

puff (pF)
an informal name for the picofarad , a unit of electric capacitance.

pulgada
the traditional Spanish inch, equal to 1/12 pie (see above). The pulgada varies from about 23.2 to 24.1 millimeters (0.913 to 0.949 inch).

pund
the Scandinavian pound, now reinterpreted as a metric unit equal to 500 grams (1.1023 pounds), like the German pfund. The traditional Swedish (Stockholm) pund was equal to about 425.1 grams (14.995 ounces).

pyron
a unit used to measure the heat flow delivered by solar radiation. The pyron is equal to one calorie per square centimeter per minute, which is exactly 697.8 watts per square meter (W/m²) if the IT calorie is used in the definition, or 697.633 W/m² if the 15° calorie is used. The name is coined fro...

qintar
a traditional Arabic unit of weight, often called the cantar in English. The qintar is the Arabic counterpart of the European quintal (see below). The unit varied in size from market to market and over time. In recent years, the qintar has been interpreted as an informal metric unit equal to 50 kilograms (110.23 pounds); traditional qintars tended ...

quadbit
a unit of information equal to 4 bits or 1/2 byte. This unit is used in telecommunications, where data is frequently transmitted in quadbits. In other contexts, the same unit is called a tetrad, a nibble, or a hexit.

quadrat- (q-)
a German prefix meaning 'square.' For example, the square kilometer is the quadratkilometer (qkm or km²) in German.

quadrumvirate
a unit of quantity equal to 4. The word was coined on the pattern of triumvirate.

quadruplet
a group of 4 items, especially 4 identical items; the word is also used for one member of the group.

quadword
a unit of information equal to 4 shortwords, 8 bytes or 64 bits. See also word .

quart (qt)
a traditional unit of volume in Scotland equal to 2 Scots pints. This is almost exactly 3 British Imperial quarts, 3.6 U.S. liquid quarts, or 3.41 liters.

quarter (qtr or Q)
an informal unit of distance equal to 1/4 mile, 2 furlongs, or 402.336 meters. This unit is used in athletics and horse racing.

quarter (qtr or Q)
an informal unit of time equal to 1/4 hour or 15 minutes. This unit occurs in informal expressions of time, such as 'quarter after 10' for 10:15.

quarter (qtr or Q)
a unit of relative time used in sports, equal to 1/4 the total playing time of a competition. A quarter is 15 minutes in American football, 12 minutes in professional basketball.

quarter (Q)
a unit of distance equal to 0.25 millimeter. See Q, above, and point .

quarter (qtr or Q)
a unit of distance equal to 1/4 yard or 9 inches (22.86 centimeters). The quarter with this definition was frequently used in cloth measurement in medieval England, and it has continued to be used on occasion down to the present day. In particular, the English ell was often described as being equal to 5 quarters. This unit is identical to the span.

quartern
a traditional English unit of weight equal to 1/4 stone, 3.5 pounds, or about 1.5876 kilogram. See also quartern-loaf, below.

quartern
a traditional unit of volume for dry goods equal to 1/4 peck or 2 quarts. This corresponds to 2.2731 liters in the British imperial system or 2.2025 liters in the U.S. system. The unit is much more common in Britain.

quartern
a traditional English unit of quantity equal to 25, or 1/4 of 100.

quartern-loaf
a traditional English unit of weight for bread. A quartern-loaf is made from a quartern of flour. The finished loaf usually weighs somewhere between 4 and 5 pounds (very roughly 2 kilograms).

quartet
a unit of quantity equal to 4.

quartile
a statistical unit equal to 25 percentiles, or 1/4 of a ranked sample.

quarto
a traditional Italian unit of volume, equal to about 73.6 liters or 2.60 cubic feet.

quarto
a traditional Portuguese unit of volume, not related to the Italian quarto nor to the English quart. The Portuguese quarto equals 2 oitavos, which is about 3.46 liters or 0.92 U.S. gallon. There are 16 quartos in a fanega, 124 in a pipa.

quarto
in English, quarto is a page size; see -mo.

quaver
a unit of relative time in music equal to 1/8 whole note or 1/16 breve.

Quevenne scale
see degree Quevenne.

quinquennium
a traditional unit of time equal to five years.

quintet
a unit of quantity equal to 5.

quintile
a statistical unit equal to 20 percentiles, or 1/5 of a ranked sample.

quintuplet
a group of 5 items, especially 5 identical items; the word is also used for one member of the group.

radar mile
the time required for a radar signal to travel a distance of one mile from the transmitter to an object, and then return to the receiver. Both ordinary (statute) and nautical miles are used: the radar statute mile is about 10.8 microseconds (µs) and the radar nautical mile is about 12.4 microseconds. A radar kilometer would be about 6.7 micros...

radian per second (rad/s)
a common unit of angular velocity. One radian per second is equal to about 9.54930 rpm. This unit has been called a strob.

radiation unit
an older name for the becquerel.

Rankine
an absolute temperature scale; see degree Rankine.

ratel
see rotl (below).

rebah
an ancient Hebrew unit of weight or mass equal to 1/4 shekel. The word means 'quarter' in Hebrew.

rebar sizes
numerical size designations for steel reinforcing bars ('rebars') used to strengthen concrete. The size number is the diameter of the rod in 8ths of an inch (1/8 inch = 3.175 millimeters); thus a rod 1 inch in diameter is a #8 rebar.

recommended dietary allowance (RDA)
units used in the U.S. to measure the amounts of certain nutrients found in foods or provided by supplements such as vitamin tablets. Each nutrient has its own RDA unit. Link: Dietary Reference Intakes from the University of Texas.

register ton (RT)
a unit of cargo capacity equal to 100 cubic feet (about 2.832 cubic meters); see ton . The symbol RT seems to be in wide use for this unit, but it is also used for the refrigeration ton (see ton ) and for the revenue ton (see below).

rehoboam
a large wine bottle holding about 4.5 liters, 6 times the volume of a regular bottle. The 'h' is silent in English pronunciation.

rep
an obsolete unit of absorbed radiation dose equal to the absorption of 93 ergs of energy per gram. This is equivalent to 0.93 rad (see above) or 9.3 milligrays (mGy). 'Rep' is an acronym for 'roentgen equivalent: physical.' The definition was made because a dose of 1 rep of beta rays was considered biologically equivalent to a dose of 1 roentgen (s...

reputed quart
see quart .

res or RES
symbol for 'resolution,' a unit defined to be the number of dots or pixels per millimeter in an image. The unit is often stated before the measurement. RES 1 is equal to 25.4 dots per inch (dpi).

retinol equivalent (RE)
a unit of dosage for retinol (vitamin A) and for related substances such as beta carotene. One RE is equivalent to 5 international units (IU), or 1.5 micrograms, of retinol. U.S. nutritional authorities recommend that an adult diet provide 1000 RE per day.

rhe
a unit of fluidity, the opposite of viscosity. The unit, pronounced 'ree', was introduced by the American chemist F.C. Bingham in 1928; he defined it as the reciprocal of the centipoise. However, it came to be used instead as the reciprocal of the poise itself, so the fluidity of a substance in rhes is 1 divided by its dynamic viscosity in poise. I...

Rhine foot or Rheinfuss
the foot unit, or fuss, traditionally used in western and northern Germany.

rhm
a unit used in physics to measure the strength of gamma rays, a form of high-energy radiation emitted by some radioactive substances. A source of strength 1 rhm produces ionization at the rate of 1 roentgen per hour at a distance of 1 meter from the source. The letters 'rhm' stand for roentgen-hour-meter.

Rhode Island
the smallest state of the U.S., Rhode Island has long served as an informal unit of area in statements such as 'an iceberg 1.5 times the size of Rhode Island has broken off from Antarctica.' Rhode Island has a land area of about 1045 square miles or 2706 square kilometers. Europeans might note that Luxembourg (2586 square kilometers) provides a com...

ri
a traditional Japanese unit of distance, sometimes called the Japanese league because it is of similar length to the European league. The ri equals 2160 ken or 12 960 shaku (the shaku being the Japanese equivalent of the foot). This is about 3927 meters or 2.44 statute miles.

Richter scale
a logarithmic scale measuring earthquake intensity. See magnitude .

ridge
a traditional Welsh unit of distance equal to 3 leaps or 20 feet 3 inches (6.1722 meters).

Riga last
a traditional British unit of volume used for measuring timber. The Riga last is named for the Latvian capital, Riga, which was a major port for the shipment of timber from Russian forests. A Riga last is 80 cubic feet (2.265 cubic meters) of square-sawn timber or 65 cubic feet (1.841 cubic meters) of round timber. See also last.