**q- [1]**- a symbol for the Latin
*quaque*, "every," often used in medical prescriptions and orders. The symbol is used in combinations such as**q8h**, "every 8 hours," or**q2d**, "every other day." **q- [2]**- a former German prefix meaning
*quadrat-*, "square," seen in combinations such as**qm**(*Quadratmeter*or square meter) and**qkm**(*Quadratkilometer*or square kilometer). The SI does not allow use of this symbol; it is rarely used in current works but often seen in older documents. **Q**- a metric unit of distance equal to exactly 0.25 millimeter (9.8425 mils)
used by typographers and page designers in Japan, in Germany, and in other
countries in preference to the traditional point
[2]. One Q is equal to about 0.71 point, a little more or less depending
on the exact definition of the point. This unit is also spelled
**kyu**. **q.d.**- abbreviation for the Latin
*quaque die*, once a day, a unit of frequency traditionally used in medical prescriptions. This notation is sometimes modified for a lesser frequency by imbedding a number of days in the middle, as in**q.2d.**, every two days. **q.h.**- abbreviation for the Latin
*quaque hora*, once an hour, a unit of frequency traditionally used in medical prescriptions. This notation is sometimes modified for a lesser frequency by imbedding a number of hours in the middle, as in**q.3h.**, every three hours. **qian**- a traditional Chinese weight unit. In modern China the qian is equal to 0.1 liang, or exactly 5 grams (0.1764 ounce).
**q.i.d.**- abbreviation for the Latin
*quater in die*, four times a day, a unit of frequency traditionally used in medical prescriptions. **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 to be a few percent larger than this. The qintar is equal to 100 rotls.
**quad**- a unit of energy equal to 10
^{15}(one U.S. quadrillion) Btu or about 1.055 exajoules (EJ) or 293.07 terawatt hours (TWh). **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**. **quadrant (quad) [1]**- a unit of angle measure equal to 1/4 circle, pi/2 radians, 90°, or 100 grads.
**quadrant (quad) [2]**- a unit of distance equal to the distance from the North Pole to the Equator. The metric system was originally designed to make this distance exactly 10 million meters. The actual meter comes close to the design, but it is a little short. In the Geodetic Reference System 1980 the value given for the quadrant is 10 001 965.7293 meters (6214.93337 miles). In principle, the quadrant is divided into 5400 nautical miles; in fact, 5400 international nautical miles equal 10 000 800 meters.
**quadrat- (q-)**- a German prefix meaning "square." For example, the square kilometer is the
quadratkilometer (qkm or km
^{2}) in German. **quadrennium**- a traditional unit of time equal to four years.
**quadrimester**- a unit of time equal to 4 months. Rare in the U.S., this unit is widely used elsewhere to describe an academic term of 4 months duration.
**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 [2].
**quantum**- a unit of relative energy used in physics. At the small scales studied in
particle physics, energy often occurs in discrete packets or units called
**quanta**. The amount of energy in a quantum depends on the frequency of the radiation carrying the energy; it is equal to the frequency (in hertz) multiplied by Planck's constant, 6.626 069 x 10^{-34}joule second (J·s). The word "quantum" is also used in other contexts where physical quantities occur as multiples of a discrete unit. For example, the quantum of electric charge is*e*, the charge on a single electron. **quart (qt) [1]**- a traditional unit of volume, so-called because it equals exactly 1/4 (one quarter) of a gallon. However, there are several possible gallons to consider: [i] in the U. S. customary measure system for liquid volumes (such as milk, for example), one quart is exactly 57.75 cubic inches, 32 fluid ounces, or approximately 0.946 3529 liters; [ii] in the U. S. customary measure system for dry volumes (pecans or strawberries, for example), one quart is 67.201 cubic inches, or approximately 1.101 221 liters; [iii] finally, in the British Imperial system, used for both liquid and dry commodities, one quart is 69.354 cubic inches, 40 fluid ounces, or exactly 1.136 5225 liters. In all cases, the quart equals 2 pints.
**quart (qt) [2]**- a unit of volume, smaller than the standard quart [1], used for
measuring wine. Wine bottles have often been called "quarts," although they
were smaller than standard quarts. In the U.S., wine was often measured by
the
**champagne quart**, which contains only 26 U.S. fluid ounces instead of 32. This is equivalent to about 46.92 cubic inches or approximately 768.912 milliliters. In Britain, wine was sold by the**reputed quart**. Following the establishment of Imperial measure, the reputed quart was fixed at 2/3 Imperial quart, which is equivalent to 1/6 Imperial gallon, exactly 26 2/3 fluid ounces, about 46.24 cubic inches, or 757.682 milliliters (this is nearly identical to the U.S. fifth). These measures have mostly disappeared in favor of the international wine bottle, which contains exactly 750 milliliters. **quart (qt) [3]**- 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 or Qr) [1]**- a traditional unit of weight equal to 1/4 hundredweight. In Britain, one quarter equals 28 pounds (12.7006 kilograms); in the United States, one quarter equals 25 pounds (11.3398 kilograms). In the U.S., "quarter" is also used informally to mean 1/4 ton, or 500 pounds (226.80 kilograms).
**quarter (qtr or Q) [2]**- a civil unit of time equal to 3 months or 1/4 year. The quarter is widely used as a time unit in business and economics. Given the layout of the Gregorian calendar in civil use throughout the world (see year [2]), the quarter varies in length from 90 to 92 days [3] depending on its starting date.
**quarter (qtr or Q) [3]**- a unit of angle measure equal to 1/4 circle; another name for a quadrant.
**quarter (qtr or Q) [4]**- a unit of angle measure, sometimes used at sea, equal to 1/4 of a compass point (see point [1]). In this use, a quarter equals 2°48'45" = 2.8125° or pi/64 = 0.049 087 radian.
**quarter (qtr or Q) [5]**- a traditional unit of volume used for measuring grain. A quarter of grain is 8 bushels (about 282 liters, based on the U.S. bushel, or 291 liters, based on the British Imperial bushel), presumably because this quantity of grain weighs roughly 1/4 ton. This unit also known traditionally as the seam.
**quarter (qtr or Q) [6]**- 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) [7]**- 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) [8]**- 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) [9]**- a unit of distance equal to 0.25 millimeter. See Q, above, and point [2].
**quarter (qtr or Q) [10]**- 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 [1]**- an old English word for a quarter of anything, "quartern" has been used to represent 1/4 of various units. In the U.S., the term seems to have been used mostly as an alternate name for the gill, which is equal to 1/4 pint or about 118.3 milliliters.
**quartern [2]**- 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 [3]**- 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 [4]**- 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 [2] of flour. The finished loaf usually weighs somewhere between 4 and 5 pounds (very roughly 2 kilograms).
**quarter tone**- a unit used in music to describe the ratio in frequency between notes. The
quarter tone, equal to 1/24 octave, is the
basic interval in a 24-tone scale. Two notes differ by a quarter tone if the
ratio in their frequencies is 2
^{1/24}= 1.0293. **quartet**- a unit of quantity equal to 4.
**quartile**- a statistical unit equal to 25 percentiles, or 1/4 of a ranked sample.
**quarto [1]**- a traditional Italian unit of volume, equal to about 73.6 liters or 2.60 cubic feet.
**quarto [2]**- 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 [3]**- 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.
**quincena**- a unit of time in Spanish-speaking countries, generally considered equivalent
to the English fortnight: two weeks or 14 days. However, the word is derived
from
*quince*, fifteen, indicating a period of two weeks that begins on one day and ends on the fifteenth day, two weeks later. Like fortnight, quincena is often used informally to refer to a period of approximately two weeks or half a month. The same unit is called the**quindicina**in Italian, the**quinzena**in Portuguese and the**quinzaine**in French. **quinquennium**- a traditional unit of time equal to five years.
**quintal (q) [1]**- a traditional unit of weight in France, Portugal, and Spain. Quintal is
also the generic name for a historic unit used in commerce throughout Europe
and the Arab world for more than 2000 years. The unit began as the Latin
*centenarius*, meaning "comprised of 100" because it was equal to 100 Roman pounds. The centenarius passed into Arabic as the cantar or*qintar*and then returned to Europe through Arab traders in the form*quintal*. The German zentner and English hundredweight are familiar forms of this same unit in northern Europe. The traditional French quintal equaled 100 livres (48.95 kilograms or 107.9 pounds), but today the word "quintal" in France usually means a larger metric unit (see next entry). The Spanish quintal is 100 libras (about 46 kilograms or 101 pounds). The Portuguese quintal is larger; it is equal to 128 libras (about 129.5 pounds or 58.75 kilograms). "Kwintal" is the English pronunciation given in standard English dictionaries, but "kintal" (closer to the Spanish pronunciation) and "kantal" (closer to the French) are also used. **quintal (q) [2]**- a common metric unit of mass equal to 100 kilograms or approximately 220.4623 pounds. Notice that the metric ton is roughly equal to its non-metric predecessors, but the metric quintal is about twice the size of the traditional quintal.
**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.
**quinzaine, quinzena**- see
**quincena**above. **quire (qr)**- a traditional unit of quantity used for counting sheets of paper. The word is from Latin, meaning "by fours." A quire was originally comprised of 24 sheets cut from four of the large sheets produced by the paper maker. In modern use a quire is often reckoned as 25 sheets, so that a ream of 20 quires is now 500 sheets rather than the traditional 480.
**Q unit**- a unit of heat energy equal to one quintillion (10
^{18}) Btu, 1000 quads, or about 1.055 zettajoules (ZJ).

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Checked and revised January 25, 2002