 daily value (DV)

a unit of nutrition used in the United States. The U.S. Food and Drug
Administration establishes recommended daily amounts of various nutrients, both
"good" ones like vitamins and "bad" ones like fat and sodium. These socalled
daily values are based on a hypothetical person, male or female, who requires a
diet of 2000 Calories per day. The results are approximate at best, since
nutritional needs vary with age, sex, and other factors. Food packages
generally carry nutritional lables specifying the amount of each nutrient
contained in a standard serving, expressed as a percentage of the daily value
(%DV).
 dalton (Da or D)

an alternate name for the unified atomic mass unit (u or amu).
 dan

a traditional Chinese weight unit, previously spelled tan in many
English works. During the European colonial era the unit was equal to 100
catties or 133.333 pounds. In modern China the dan is equal to 100 jin, which
is exactly 50 kilograms (110.231 pounds). The dan is the Chinese equivalent of
the European quintal or hundredweight.
 data mile

a unit of distance used in radar technology. The data mile equals exactly 6000
ft or 1828.8 meters; this is equivalent to about 1.137 statute (ordinary) miles
or 0.9875 nautical miles. U.S. military radar equipment is often calibrated in
data miles.
 deadweight ton (dwt)

a traditional unit of weight or mass used in the shipping industry. The
deadweight tonnage of a ship is the difference between its weight when
completely empty and its weight when fully loaded. This includes the weight of
everything portable carried by the ship: the cargo, fuel, supplies, crew, and
passengers. The deadweight ton is traditionally equal to the British ("long")
ton of 2240 pounds (1016.047 kilograms). However, more often it is being taken
to equal the metric ton (1000 kilograms, or 2204.623 pounds).
 deca (da)

a metric prefix meaning 10, derived from the Latin word for ten, decem.
The Greek form deka is also used, and it has the advantage of avoiding
confusion with deci, one tenth. The International Bureau of Weights and
Measures (BIPM) specifies deca for the prefix and da for the symbol. In its
interpretation of the International System (SI) for U.S. use, the U.S. National
Institute of Standards and Technology (NIST) recommends deka for the spelling
of the prefix. Following NIST, this dictionary uses the spelling deka.
 decade

a traditional unit of quantity equal to 10. Also called the decad. 10
years, 10 days or 1/3 month. In medieval English this unit was anglicized
as the dicker.
 decamillion

the number 10 million (10^{7}).
 decennium

a unit of time equal to 10 years; another name for a decade. The census in the
U.S. is called decennial because it is taken every ten years.
 deci (d)

a metric prefix meaning one tenth, or 0.1. The prefix is derived from the Latin
word decimus for a tenth.
 decibar (dbar)

a metric unit of pressure equal to 0.1 bar or 10 kilopascals. One decibar
equals 75.006 torr, or 1.450 pounds per square inch (lbf/in^{2} or
psi). The decibar is often used to measure the pressure of seawater, because an
increase of 1 decibar in pressure corresponds closely to an increase of 1 meter
in depth.
 decibel (dB)

a customary logarithmic measure most commonly used (in various ways) for
measuring sound. The human ear is capable of detecting an enormous range of
sound intensities. Experiment shows that when humans perceive one sound
to be twice as loud as another, in fact the louder sound is about ten times as
intense as the fainter one. For this reason, sound is measured on logarithmic
scales. Informally, if one sound is 1 bel (10 decibels) "louder" than another,
this means the louder sound is 10 times louder than the fainter one. A
difference of 20 decibels corresponds to an increase of 10 x 10 or 100 times in
intensity.

For sound intensity (the power of the sound waves per unit of area) 0 decibels
is equal 1 picowatt per square meter; this corresponds approximately to the
faintest sound that can be detected by a person who has good hearing. A quiet
room has a normal sound intensity of around 40 decibels, ten thousand times
louder than the faintest perceptible sound, and a thunderclap may have an
intensity of 120 decibels, a trillion times louder than the faintest sound.
 decigram (dg)

a metric unit of mass equal to 100 milligrams or about 1.5432 grains.
 decile

a statistical unit equal to 10 percentiles, or 1/10 of a ranked sample.
 deciliter (dl or dL)

a common metric unit of volume equal to 0.1 liter or 100 cubic centimeters. A
deciliter contains 6.10237 cubic inches, 3.38140 U.S. fluid ounces, or 3.519
British fluid ounces. The deciliter is similar in size to the gill, an old
English unit of volume.
 decimeter (dm)

a fairly common metric unit of distance equal to 10 centimeters or 3.9370
inches. The decimeter is very close to the hand, a traditional English unit.
 decimillimeter (dmm)

a metric unit of distance equal to 0.1 millimeter (10^{4} meter) or
about 3.937 mils. The use of compound prefixes such as decimilli is not
permitted in the SI.
 decipol

an empirical unit of indoor odor intensity introduced by the Danish
environmental scientist P.O. Fanger in 1988.
 decitex (dtex)

a common metric unit of yarn density equal to 0.1 tex, 0.9 denier (see below),
or 0.1 milligram per meter. This unit was previously called the drex.
 decitonne (dt or dtn)

a metric unit of mass or weight equal to 100 kilograms (220.4623 pounds). This
unit is becoming common in international trade; it is the same as the Russian
centner, the German doppelzentner, and the French metric quintal.
 degree (° or deg)

the standard unit of angle measure, equal to 1/360 circle, 60 minutes, 3600
seconds, or about 0.017 453 293 radian. So far as we know, this unit was
introduced by the Greek geometer Hipparchus of Nicaea (125 BC), who developed
the first trigonometric tables.

A unit of distance sometimes used at sea, equal to 60 nautical miles,
approximately 69.05 statute miles, or 111.12 kilometers. This distance is the
average length of one degree of latitude. Because the Earth is not exactly
spherical, a degree of latitude actually varies from about 68.7 miles at the
Equator to 69.4 miles at the poles. One degree of longitude is about 69.17
miles at the Equator.

Any of the various units of temperature. In the U.S., the unmodified unit
"degree" generally means the degree Fahrenheit; in other countries, it means
the degree Celsius.

A unit measuring the hardness of water. Water is called "hard" if it contains a
high concentration of mineral salts, especially calcium carbonate. This
concentration can be expressed clearly in parts per million (ppm) or in
milligrams per liter (mg/L).

Various scientific quantities, especially specific gravity and viscosity, have
been measured in "degrees" based on the readings of particular instruments. The
degree scales of Baumé (see below) and Beck, and many others, have been used in
measuring specific gravity, and the scales of Engler and MacMichael are common
in the measurement of viscosity.

The percentage of alcohol, by volume, present in a mixture. In winemaking, for
example, a 13° wine is 13% alcohol by volume (13% v/v), also called the degree
GayLussac (° GL) after the French chemist JosephLouis GayLussac
(17781850).

A unit used in mathematics to describe algebraic expressions. The degree of an
expression having a single variable is the highest exponent (or power) to which
that variable appears. If the expression has more than one variable, then the
degree is the highest total exponent of the individual terms, where in each
term the exponents of the different variables are added. Thus x^{2}y^{4}z^{3}
is a term of degree 9.
 degree API (°API)

a unit invented by the American Petroleum Institute (API) to measure the
specific gravity, or one might say the "lightness," of petroleum. Lighter oils
are more valuable, so the API scale gives them higher readings than heavier
oils. If G is the specific gravity of the petroleum at temperature
60 °F (15.56 °C), the API degree rating is equal to (141.5/G)  131.5
degrees.
 degree Baumé (°B or °Bé)

a unit of relative density, as read on a type of hydrometer invented by the
French chemist Antoine Baumé (17281804). Two scales are used, depending on
whether the liquid is lighter than water or heavier than water. For lighter
liquids, the relative density d in degrees Baumé is related to specific
gravity G by the formula d = (144.3 / G)  144.3.
 degree Celsius (°C)

a metric unit of temperature. The Celsius temperature scale is named for the
Swedish astronomer and physicist Anders Celsius (17011744), who used a similar
scale. The freezing point of water (at one atmosphere of pressure) was
originally defined to be 0 °C, while the boiling point is 100 °C. Thus the
Celsius degree is 1/100 of the difference between these two temperatures. For
practical purposes this is equivalent to the original definition. See also
degree Fahrenheit, Kelvin. Please see Unit Table or Converter
 degree centigrade (°C)

an older name for the degree Celsius. About 1850 scientists began calling the
unit "degree Celsius".
 degree day

a unit used in meteorology and engineering to measure the demand for heating or
cooling. In the United States, it's agreed that 65 °F (18.3 °C) is the critical
outside temperature; below this tempeature heating is needed and above it
cooling is needed. The number of degree days recorded on a given date is equal
to the difference between 65 and the mean temperature for that date (figured as
the average of the highest and lowest temperatures). If the mean temperature is
above 65, cooling degree days (CDD) are recorded; if it is below 65, heating
degree days (HDD) are recorded.
 degree Dornic (°D)

a measure of the acidity of milk. Each degree Dornic is equivalent to 0.01%
lactic acid in the milk. Normal values are around 15.
 degree EBC (°EBC)

a unit used in Europe to measure the color of beer. EBC is an abbreviation for
European Brewing Convention. EBC degrees are related to the Lovibond degrees
used in the U.S. by the approximate formula °EBC = (°L * 2.65)  1.2.
 degree Fahrenheit (°F)

a unit of temperature used in the United States. The unit was defined by
the German physicist Daniel G. Fahrenheit (16861736), who also invented the
mercury thermometer. Fahrenheit set 0° at the coldest temperature he could
conveniently achieve using an ice and salt mixture, and it is said he intended
to set 96° as the temperature of the human body. On this scale, the
freezing point of water (at normal sea level atmospheric pressure) turned out
to be about 32 °F and the boiling point about 212 °F. The scale was precisely
defined by these two temperatures: °F = 9/5 °C + 32.
 degree Kelvin (°K)

In the International System, temperatures on the absolute temperature scale are
stated in kelvins, not in degrees Kelvin.
 degree KMW (°KMW)

a unit used in Austria to measure the sugar content of must, the unfermented
liquor from which wine is made.
 degreeLovibond (°L)

a unit used in the U.S. to measure the color (really the darkness) of beer and
honey. The scale is openended, but most readings fall between 1 (a very light
gold, or yellow) and 25 (a very dark brown).
 degree MacMichael (°McM)

a unit used to measure the viscosity, or thickness, of chocolate. Typical
values range from around 60 °McM (very thin chocolates suitable for pouring
into molds) to around 190 °McM (very thick chocolates).
 degree Oechsle (°Oe)

a unit used in Germany and Switzerland to measure the sugar content of must,
the unfermented liquour from which wine is made. One degree Oechsle (or Öchsle)
is roughly equivalent to 0.2% sugar by weight. This unit is related legally to
°KMW by the formula °Oe = °KMW * ([.022 * °KMW] + 4.54).
 degree Plato (°P)

a unit measuring sugar content, especially of the wort, the unfermented liquour
from which beer is made. Named for a German chemist, one degree Plato
represents a sugar content equivalent to 1% sucrose by weight. In Europe,
beer is often taxed either by the degree Plato or by the actual alcohol
content. There is no precise conversion between these quantities, but for tax
purposes it is often assumed that 1% alcohol (1 degree) is equivalent to 2.5
degrees Plato; that is, 1 degree Plato is legally equivalent to 0.4% alcohol.
 degree Quevenne (°Q)

a unit measuring the density of milk. 1 °Quevenne represents a difference in
specific gravity of 0.001, so, for example, 20 °Q milk has specific density
1.020.
 degree Rankine (°R)

a traditional unit of absolute temperature. 1 °Rankine represents the same
temperature difference as 1 °Fahrenheit, but the zero point of the scale is set
at absolute zero. This means the Rankine temperature is 459.67° plus the
Fahrenheit temperature. 1 °Rankine is equal to exactly 5/9 kelvin. The unit is
named for the British physicist and engineer William Rankine (18201872).
 degree Réaumur (°r)

a unit of temperature formerly used in Europe. The Réaumur temperature scale is
named for the French scientist RenéAntoine Ferchault de Réaumur (16831757).
It is similar to the Celsius scale in having its zero point at the freezing
temperature of water, but the interval between the freezing and boiling
temperatures of water equals 80 °r instead of 100 °C. Therefore, 1 °r equals
1.25 °C or 2.25 °F.
 degree SoxhletHenkel (°SH)

a measure of the acidity of milk. Each degree SoxhletHenkel is equivalent to
0.0225% lactic acid in the milk. Normal values are around 7.
 degree Therner (°Th)

a measure of the acidity of milk. Each degree Therner is equivalent to 0.009%
lactic acid in the milk. Normal values are around 17.
 degree Twaddle (°Tw)

a unit measuring the specific gravity of liquids denser than water. 1 °Twaddle
represents a difference in specific gravity of 0.005 or 1/200, so a liquid of
specific gravity S is measured at 200(S  1) °Tw. For milk, 1 °Twaddle equals 5
°Quevenne (see above).
 deka (da)

a metric prefix meaning 10, taken directly from the Greek word for ten, deka.
The Latin spelling deca is also used (see deca above).
 dekagram or decagram (dag)

a common metric unit of mass, the dekagram is frequently used in European food
recipes. One dekagram is equal to 10 grams, 0.01 kilogram, or 0.352 739 66
ounce. The symbol dkg sometimes used for this unit is incorrect.
 dekaliter or decaliter (daL or dal)

a metric unit of volume equal to 10 liters and comparable to the English peck.
The dekaliter is equal to about 2.641 72 U.S. liquid gallons, 1.135 10 U.S.
pecks, or 2.199 69 British imperial gallons (1.099 85 British pecks). The
symbol dkL sometimes used for this unit is incorrect.
 dekameter or decameter (dam)

a common metric unit of distance equal to 10 meters (about 32.8084 feet).
 dekanewton or decanewton (daN)

a fairly common metric unit of force equal to 10 newtons. The dekanewton is
equal to 1 megadyne, to 1.019 716 kilograms of force (kgf) or kiloponds (kp),
to 2.248 09 pounds of force (lbf), and to 72.3301 poundals. In engineering, the
dekanewton is a convenient substitute for the kilogram of force or kilopond,
since it is nearly equal to those units.
 dekan

a unit of angle measure equal to 10° or 1/36 circle. The ancient Egyptians
divided the circle of the Zodiac into 36 divisions, which the Greeks called
dekans.
 dekare or decare

a metric unit of area equal to 10 ares, that is, 1000 square meters or 0.1
hectare. In English units, the dekare equals approximately 10 763.91 square
feet, 1195.99 square yards, or 0.247 105 acres.
 dekatherm or decatherm (DTH)

a unit of energy equal to 10 therms, 1 million Btu, or about 1.055 057
gigajoules (GJ).
 demi

a traditional prefix meaning 1/2. The prefix is derived from the Latin dimedius,
meaning a cut in the middle of something.
 demisemiquaver

a unit of relative time in music equal to 1/32 whole note or 1/64 breve.
 dessertspoon or dessertspoonful (dsp or dssp)

a unit of volume sometimes used in food recipes. The dessertspoon is equal to 2
teaspoons; this is roughly equivalent to 10 milliliters in the U.S. In the
metric world, a measuring spoon holding exactly 10 milliliters is often called
a dessertspoon.
 dessiatina

a unit of land area in Russia equal to 2400 square sadzhens. It equals about
1.0925 hectare or 2.6996 acres.
 devil's dozen

an alternate name for the baker's dozen, a traditional unit of quantity equal
to 13. This name reflects the longstanding association of the number 13 with
bad luck or evil.
 dex

a logarithmic unit being used in astronomy. Originally, dex was a convenient
function defined by dex (x) = 10^{x}. But the notation is
now being used after the exponent in expressions such as .043 dex, meaning 10^{.043}.
Thus 1 dex equals a factor of 10, making the dex identical to the bel. The name
"dex" is a contraction of "decimal exponent."
 dhur

a unit of land area in South Asia, equal to 1/20 kattha or 1/400 bigha. Like
the bigha, the dhur varied in size from region to another. In Nepal, where the
unit is still in use, the dhur equals about 16.9 square meters or 20.2 square
yards.
 diamond

a mysterious marking on many tape measures in the U.S. The diamonds mark a
distance unit equal to exactly 8/5 feet (19.2 inches or 48.768 centimeters).
 digit

an old unit of distance equal to the width of a person's finger. Used in
all the ancient civilizations of the Middle East and Mediterranean, the digit
was equal to 0.75 inch or 19 millimeters with only the smallest variations.
Typically, there were 4 digits in a palm, 16 in a foot, and 24 (sometimes 28)
in a cubit. The word digit is from the Latin word for a finger or toe, digitus.
It is used as any one in ten Arabic Numbers.
 dimension (dim)

a mathematical unit measuring the number of independent directions in a set or
space. The ordinary space we live in has 3 dimensions. The theory of
relativity is set in a "spacetime" having 4 dimensions, and higher dimensional
spaces are frequently used in science and economics. In addition,
mathematicians have developed several methods for assigning fractional
dimensions to certain complex sets.
 diraa

a traditional Egyptian unit of distance equal to about 58 centimeters (22.8
inches).
 dog year

an informal unit of time equal to 1/7 of a normal, or "human" year. According
to folklore, dogs age 7 times faster than humans.
 doublet

another name for a pair.
 double word or doubleword

a unit of information equal to 2 shortwords, 4 bytes or 32 bits.
 dozen

a familiar unit of quantity equal to 12. Division into units of 12 rather than
10 has the advantage that 12 can be evenly divided into halves, thirds, or
quarters. For this reason, units of 12 have been common since the earliest
civilizations of the Middle East. "Dozen" comes from an old French word dozaine
related to the Latin word duodecem, "twelve."
 dpi

an abbreviation for "dots per inch," remains in use even though individual
picture elements are now called pixels rather than dots.
 drachma

a traditional unit of weight in Greece and the eastern Mediterranean. The
drachma was a Greek coin, and the unit was originally the weight of the coin.
In ancient times this was about 4.3 grams, but more recent versions are about
3.2 grams, 49.3 grains, or 0.113 ounce avoirdupois. There is also a traditional
Dutch weight unit of the same name, but it is somewhat larger: 3.906 grams,
60.28 grains, or 0.1374 ounce avoirdupois. Compared to a similar English unit,
the Greek drachma is about 2.5 pennyweight and the Dutch is almost exactly 3
pennyweight.
 drachme

a traditional unit of weight in France and Germany, generally between 3.7 and
3.9 grams.
 dram

a unit of weight in the traditional avoirdupois system, equal to 1/16 ounce or
1/256 pound. One dram equals about 1.7718 gram. The word dram comes from a
Latin weight unit, the dragma, and derives ultimately from the Greek drachme,
meaning a handful.

a unit of weight in the traditional system of English apothecaries, equal to 60
grains, 3 scruples, 1/8 troy ounce, or approximately 3.8879 gram. The
apothecaries' dram is sometimes abbreviated dr. ap. to distinguish it
from the avoirdupois dram.

a traditional unit of volume. See fluid dram.
 drex

a unit traditionally used in the textile industry to measure the density of a
single fiber of yarn. One drex equals a density of one gram per 10 kilometers
of length, or 1 microgram per centimeter (µg/cm). Since 1 drex equals 0.1 tex,
the unit is now called the decitex (dtex)
 drill sizes

traditional drill sizes are numbers 180, with larger numbers indicating
smaller drills. Number 1 has diameter 0.2280 inch and number 80 has diameter
0.0135 inch. Larger sizes are designated by letters or by specifying the
diameter directly in 64ths of an inch. The metric drill size is the diameter in
millimeters.
 drink

a unit measuring the alcohol content of beverages, used in describing the
medical effects of alcohol. U.S. physicians generally consider one drink equal
to 0.5 U.S. fluid ounces of alcohol; the appropriate metric equivalent would be
15 milliliters. In U.S. fluid units, one drink corresponds to about 4 ounces of
wine or 1.25 ounces of whiskey.
 drap

a traditional unit of weight in Scotland, equal to 1/16 Scots ounce or about
1.9 grams. Sometimes spelled drop, this unit was the Scottish
counterpart of the English dram.
 drop (gtt)

a unit of volume used in pharmacy. Now that prescriptions are written in metric
units, the pharmacist's drop is equal to exactly 0.05 milliliter (20 drops/ml).
In hospitals, intravenous tubing is used to deliver medication in drops of
various sizes ranging from 10 drops/ml to 60 drops/ml. The traditional
abbreviation is from the Latin gutta, drop. Originally, gt was
the symbol for a single drop, with gtt being the plural.

a informal unit of volume used in recipes. According to some older kitchen
references, 24 drops = 1/4 teaspoon; with U.S. definitions this makes the drop
equal to 1/576 fluid ounce or about 0.051 milliliter, comparable to the
pharmacist's drop.
 drought severity category (D)

a measure of drought severity developed by the U.S. National Drought Mitigation
Center and used widely by other agencies in the U.S. Categories are
denoted D0D5, with higher numbers indicating more severe drought.
 drum

a unit of volume sometimes used in the oil trade. The traditional standard drum
of oil contains 55 U.S. gallons or about 208.198 liters. One 55gallon drum
equals 1.3095 barrels. In the metric world, drums of 200 liters, 205 liters,
and 208 liters are in use as substitutes for the traditional size.
 dry pint, dry quart

common names for the U.S. pint and quart units used for dry commodities, used
to distinguish these units from the pint and quart used for liquids. The dry
units are equal to about 1.163 647 times the corresponding liquid units.
 duet or duo

a traditional unit of quantity equal to 2. The word duet is a French
version of the Italian duo, two.
 dunum or donum

a traditional unit of land area in the Middle East and the Balkans. The unit is
of Turkish origin, but it seems to be obsolete in modern Turkey. As it is
commonly used today in Israel and Palestine and in Croatia and other areas of
the former Yugoslavia, the dunum is a metric unit equal to 1000 square meters
or 0.1 hectare (about 0.2471 acre). In Mesopotamia and Arabia, the dunum
was a larger unit, traditionally in the range of 2500 to 4000 square meters. In
modern Iraq, the dunum is now standardized at 2500 square meters (about 0.6179
acre).
 duro, durometer

a measure of the hardness of plastic, rubber, or similar material, made an
instrument called a durometer. These instruments test the material with a steel
pin, and the depth of the indentation made by the pin is read by a calibrated
spring meter.
