 baht

a weight unit in Thailand, now equal to exactly 15 grams, or 0.5291 unce. The
baht, originally the weight of a silver coin of the same name, is used to
measure the weight of precious metals.
 bale

a commercial unit of weight for shipments of cotton. In the United States, one
bale of cotton, formerly equal to 500 pounds (226.80 kg), is now equal to 480
pounds (217.72 kg). The British used the Egyptian bale, formerly equal to 750
pounds (340.19 kg) but now equal to 720 pounds (326.59 kg).
 bar

a metric unit of atmospheric pressure, equal to one million dynes per square
centimeter, 100 kilopascals, 750.062 torr, 1.019 72 kilograms of force per
square centimeter (kgf/cm^{2}), or about 14.503 78 pounds per square
inch (lbf/in^{2} ). One bar is just a bit less than the average
pressure of the Earth's atmosphere, which is 1.013 25 bar.
 barrel

A commercial unit of volume used to measure liquids such as beer and wine. The
official U. S. definition of the barrel is 31.5 gallons, which is about 4.211
cubic feet or 119.24 liters. There are other official barrels, defined in
certain U.S. states; most of them fall in the general range of 3040 gallons. A
barrel of beer in the U.S., for example, is usually 31 U.S. gallons (117.35
liters). The standard symbol bbl.

A commercial unit of volume used to measure petroleum. By international
agreement a barrel of petroleum equals 42 U. S. gallons, which is about 158.987
liters. The symbol bo (barrel of oil) is used for this unit in the
petroleum industry.
A commercial unit of volume used to measure dry commodities such as apples. The
U. S. dry barrel, established by Congress in 1912, is 105 dry quarts, which is
about 4.083 cubic feet or 115.63 liters.
 barrel bulk

a commercial unit of volume equal to exactly 5 cubic feet or 0.141 584 cubic
meters. There are exactly 8 barrels bulk in a freight ton and 20 in a register
ton.
 baud (Bd)

a unit used for measuring the rate of data transmission over telegraph or
telephone lines. The baud rate is the number of times per second the signal
carrying the communication varies in strength or frequency. If the signal has
only two states (on or off) then the baud rate is the same as the transmission
rate in bits per second. The baud is named for the French telegraph
engineer J. M. E. Baudot (18451903), the inventor of the first teleprinter.
 BB

a common shot pellet size in the U.S.; the diameter of BB shot is used
informally sometimes as a distance unit. BB shot has a diameter of 0.180 inch
(4.572 mm).
 BC, BCE

abbreviations for "before Christ" and "before common era".
 beat

a unit of time equal to 0.001 day or 86.4 seconds. "Metric time," meaning
decimalized time, is an idea dating back at least to the French Revolution of
the 1790's. In most metric time proposals, the day is divided into 10 metric
hours, each metric hour into 100 metric minutes (or beats), and
each metric minute into 100 metric seconds (sometimes called blinks).
 bell

an old unit of time. On ships at sea, a practical measure of time is the
watch, a period of 4 hours. The watch is divided into 8 bells, so one bell
equals 1/2 hour or 30 minutes.
 bhp

abbreviation for brake horsepower. The brake horsepower of an engine is
the effective power output, sometimes measured as the resistance the engine
provides to a brake attached to the output shaft.
 bi

a common English prefix meaning 2. bi means "every two." Thus a biweekly
payroll is paid once every two weeks, a bimonthly magazine is published
once every two months, and the U.S. House of Representatives is elected biennially
(every two years).
 bicron (µµ)

an obsolete metric unit of distance, defined as 10^{12} meter or 10^{6}
micron. This distance is now called a picometer (pm). The name is a reference
to the double prefix in "micromicron."
 biennium

a unit of time equal to two years. Many U.S. states, elect legislators
every two years and adopt budgets for this twoyear period, called a biennium.
 bigha

a traditional unit of land area in South Asia. The bigha varies in size from
region to another; in India it is generally less than an acre (0.4 hectare). In
Nepal the bigha equals about 0.677 hectare (1.67 acres). The bigha was divided
into 20 katthas, and each kattha contained 20 dhurs.
 billennia

a new word meaning "billions of years," billennia is appearing informally in
science writing in phrases such as "countless billennia" or "the billennia of
evolutionary time."
 bit

the basic unit of the amount of data. Each bit records one of the two possible
answers to a single question: "0" or "1," "yes" or "no," "on" or "off."
The word "bit" was coined by the American statistician and computer scientist
John Tukey in 1946 as an acronym for binary digit.
 bit per second (b/s or bps)

a common unit of data transmission rate in computer science. The symbol bps is
often pronounced "bips."
 blink

a unit of time equal to 10^{5} day or exactly 0.864 second. This unit
is also called the metric second. An actual eye blink takes less than
half as much time as this unit.
 block

an informal unit of distance popular in the U.S. A block is the average
distance between street intersections in the rectangular street grids common in
most American cities.
 boiler horsepower

a traditional unit measuring the power delivered by a boiler. The boiler
horsepower is defined to be the power required to convert 30 pounds (13.61
kilograms) per hour of water at 100 °F (37.78 °C) to saturated steam at a
pressure of 70 pounds per square inch gauge (482.6 kilopascals gauge).
 bottle

a unit of volume. Like actual bottles, this unit varies according to the nature
of the contents. For a long time in the U.S., a bottle of milk was 1 quart (1/4
gallon or 946.36 milliliters), a bottle of whiskey was 1 fifth (1/5 gallon or
757.1 milliliters), and a bottle of champagne was 2/3 quart (1/6 gallon or
630.91 milliliters).
 box

a unit of volume, usually informal but standardized in certain industries. In
the U.S., a box of citrus fruit contains 1.6 bushels (56.383 liters).
 bpd

abbreviation for barrels per day, a unit of production used in the petroleum
industry.
 bpm

abbreviation for beats per minute, the common unit of tempo in music. The same
symbol is used in medicine for heart rates and also for respiration rates
(breaths per minute). Technically, 1 bpm is equal to 1/60 hertz.
 brace

another name for a pair. The word is used mostly by hunters, who may speak of a
brace of partridges or a brace of shotguns. Derived from the Latin word bracchia
for both arms, it literally means "one for each arm."
 brake horsepower (bhp)

the effective power output of an engine, sometimes measured as the resistance
the engine provides to a brake attached to the output shaft.
 breadth

another name for a span(9 inches or 22.86 centimeters). This unit is
traditionally used to measure the dimensions of flags.
 breve

the standard unit of relative time in music, equal to the time length of 2
whole notes. Although this is the longest interval in musical notation, the
word comes from the Latin brevis, brief. The breve is equal to 2
semibreves, 4 minims, 8 crotchets, or 16 quavers.
 bril

a unit used to express the "brilliance" or subjective brightness of a source of
light.
 Brinell hardness (HB or BHN)

a measure of the hardness of a metal introduced by J. A. Brinell in 1900.
 British thermal unit (BTU)

a unit of heat energy defined as the amount of heat required to raise the
temperature of one pound of water by one degree Fahrenheit. In America the
British thermal unit is sometimes called the heat unit. Using the current
definition of the calorie (the IT calorie), one Btu equals approximately
778.169 foot pounds, 1.055 056 kilo joules or 0.293 071 watt hour.
 bundle

a unit of quantity for paper, equal to 2 reams or 40 quires. This would be 960
sheets using the old definition of 24 sheets per quire, or 1000 sheets using
the newer quire of 25 sheets.

a traditional unit of length for yarn, equal to 20 hanks. For cotton yarn, a
bundle contains 16,800 yards (about 15.362 kilometers). For wool, a bundle
contains 11,200 yards (10.241 kilometers).

in the construction trades, a bundle is a package of shingles. Asphalt shingles
are often sold in bundles of 27, with 3 bundles per square, but the heavier
cedar shingles generally require 5 bundles per square.
 bushel (bu)

A traditional unit of volume used for measuring dry commodities such as grains
and fruits. One U.S. or Winchester bushel equals 4 pecks or 32 (dry) quarts;
this is a volume of 2150.42 cubic inches or about 1.2445 cubic feet, and
represents the volume of a cylindrical container 18.5 inches (47.0 cm) in
diameter and 8 inches (20.3 cm) deep. The U. S. bushel holds about 35.239 07
liters.


A unit of volume in the British imperial system equal to 8 imperial
gallons, or 2219.36 cubic inches (1.2844 cubic feet). The imperial bushel holds
about 36.369 liters.

A commercial unit of weight for grains and other bulk commodities. For
example, in the United States a bushel of wheat equals 60 pounds (27.216 kg), a
bushel of barley 48 pounds (21.772 kg), a bushel of oats 32 pounds (14.515 kg),
and a bushel of rye 56 pounds (25.401 kg).
 butcher

a unit of volume for beer in South Australia. A butcher of beer is a glass
holding 200 milliliters. This is called a glass or a seven in other parts of
Australia.
 Bya or bya

a common abbreviation for "billion years ago."
 byte (B)

a unit of information or data. The byte is a unit of addressable memory, and
its size can vary depending on the machine or the computing language. In most
contexts, the byte is equal to 8 bits (or 1 octet). This means that a
byte has 2^{8} = 256 possible states. The unit was named by IBM
engineer Werner Buchholz in 1956.
