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Info from units that should be included

[edit]
are                  100 m^2
litre                 1000 cc      The litre was defined in 1901 as the
old litre              1.000028 dm^3  space occupied by 1 kg of pure water at
l                     liter        the temperature of its maximum density

under a pressure of 1 atm. This was supposed to be 1000 cubic cm, but it was discovered that the original measurement was off. In 1964, the litre was redefined to be exactly 1000 cubic centimeters.

mho                   siemens   Inverse of ohm, hence ohm spelled backward
galvat                ampere    Named after Luigi Galvani
angstrom              1e-10 m   Convenient for describing molecular sizes
xunit                 1.00202e-13 meter  Used for measuring wavelengths
siegbahn              xunit            of X-rays.  It is defined to be

1|3029.45 of the spacing of calcite planes at 18 degC. It was intended to be exactly 1e-13 m, but was later found to be off slightly.

fermi                 1e-15 m   Convenient for describing nuclear sizes

Nuclear radius is from 1 to 10 fermis

barn                  1e-28 m^2  Used to measure cross section for

particle physics collision, said to have originated in the phrase "big as a barn".

shed                  1e-24 barn  Defined to be a smaller companion to the

barn, but it's too small to be of much use.

brewster              micron^2/N  measures stress-optical coef
diopter               /m        measures reciprocal of lens focal length
fresnel               1e12 Hz   occasionally used in spectroscopy
shake                 1e-8 sec
svedberg              1e-13 s   Used for measuring the sedimentation

coefficient for centrifuging.

gamma                 microgram
lambda                microliter
spat                  1e12 m    Rarely used for astronomical measurements
preece                1e13 ohm m  resistivity
planck                J s       action of one joule over one second
sturgeon              /henry    magnetic reluctance
daraf                 1/farad   elastance (farad spelled backwards)
leo                   10 m/s^2
poiseuille            N s / m^2  viscosity
mayer                 J/g K     specific heat
mired                 / microK  reciprocal color temperature.  The name

abbreviates micro reciprocal degree.

metricounce           25 g
mounce                metricounce
finsenunit            1e5 W/m^2  Measures intensity of ultraviolet light

with wavelength 296.7 nm.

fluxunit              1e-26 W/m^2 Hz  Used in radio astronomy to measure

the energy incident on the receiving body across a specified frequency bandwidth. [12]

jansky                fluxunit  K. G. Jansky identified radio waves coming
Jy                    jansky    from outer space in 1931.
pfu                  / cm^2 sr s  particle flux unit -- Used to measure

rate at which particles are received by a spacecraft as particles per solid angle per detector area per second. [18]

katal                 mol/sec   Measure of the amount of a catalyst.  One
kat                   katal       katal of catalyst enables the reaction

to consume or produce on mol/sec.

minute                60 s
min                   minute
hour                  60 min
hr                    hour
day                   24 hr
d                     day
da                    day
week                  7 day
wk                    week
sennight              7 day
fortnight             14 day
blink                 1e-5 day  Actual human blink takes 1|3 second
ce                    1e-2 day
cron                  1e6 years
watch                 4 hours   time a sentry stands watch or a ship's

crew is on duty.

bell                  1|8 watch  Bell would be sounded every 30 minutes.
circle                2 pi radian
degree                1|360 circle
arcdeg                degree
arcmin                1|60 degree
arcminute             arcmin
arcsec                1|60 arcmin
arcsecond             arcsec
quadrant              1|4 circle
quintant              1|5 circle
sextant               1|6 circle
pulsatance            radian / sec
gon                   1|100 rightangle  measure of grade
grade                 gon
centesimalminute      1|100 grade
centesimalsecond      1|100 centesimalminute
milangle              1|6400 circle    Official NIST definition.

Another choice is 1e-3 radian.

pointangle            1|32 circle  Used for reporting compass readings
centrad               0.01 radian  Used for angular deviation of light

through a prism.

mas                   milli-arcsec  Used by astronomers
seclongitude          circle (seconds/day)  Astronomers measure longitude

(which they call right ascension) in time units by dividing the equator into 24 hours instead of 360 degrees.

Solid angle measure
sphere                4 pi sr
squaredegree          1|180^2 pi^2 sr
squareminute          1|60^2 squaredegree
squaresecond          1|60^2 squareminute
squarearcmin          squareminute
squarearcsec          squaresecond
sphericalrightangle   0.5 pi sr
octant                0.5 pi sr 
Concentration measures
percent               0.01
mill                  0.001    Originally established by Congress in 1791

as a unit of money equal to 0.001 dollars, it has come to refer to 0.001 in general. Used by some towns to set their property tax rate, and written with a symbol similar to the % symbol but with two 0's in the denominator. [18]

proof                 1|200    Alcohol content measured by volume at

60 degrees Fahrenheit. This is a USA measure. In Europe proof=percent.

ppm                   1e-6
partspermillion       ppm
ppb                   1e-9
partsperbillion       ppb      USA billion
ppt                   1e-12
partspertrillion      ppt      USA trillion
karat                 1|24     measure of gold purity
caratgold             karat
gammil                mg/l
basispoint            0.01 %   Used in finance
fine                  1|1000   Measure of gold purity 
The pH scale is used to measure the concentration of hydronium (H3O+) ions in
a solution.  A neutral solution has a pH of 7 as a result of dissociated
water molecules.
pH     pH(x) [;mol/liter] 10^(-x) mol/liter ; (-log(pH liters/mol))
Temperature
Two types of units are defined: units for computing temperature differences
and functions for converting absolute temperatures.  Conversions for
differences start with "deg" and conversions for absolute temperature start
with "temp".
°F          tempF(x) [;K] (x+(-32)) degF + stdtemp ; (tempF+(-stdtemp))/degF + 32
°K           tempC(x) [;K] x K + stdtemp ; (tempC +(-stdtemp))/K  In 1741 Anders Celsius
°C            tempcelsius(x) [;K] tempC(x); ~tempC(tempcelsius)  introduced a temperature
degcelsius            K        scale with water boiling at 0 degrees and
                          K        freezing at 100 degrees at standard

pressure. After his death the fixed points were reversed and the scale was called the centigrade scale. Due to the difficulty of accurately measuring the temperature of melting ice at standard pressure, the centigrade scale was replaced in 1954 by the Celsius scale which is defined by subtracting 273.15 from the temperature in Kelvins. This definition differed slightly from the old centigrade definition, but the Kelvin scale depends on the triple point of water rather than a melting point, so it can be measured accurately.

fahrenheit         5|9 degC  Fahrenheit defined his temperature scale
                       5|9 degC  by setting 0 to the coldest temperature

he could produce in his lab with a salt water solution and by setting 96 degrees to body heat. In Fahrenheit's words:

Placing the thermometer in a mixture of sal ammoniac or sea salt, ice, and water a point on the scale will be found which is denoted as zero. A second point is obtained if the same mixture is used without salt. Denote this position as 30. A third point, designated as 96, is obtained if the thermometer is placed in the mouth so as to acquire the heat of a healthy man." (D. G. Fahrenheit, Phil. Trans. (London) 33, 78, 1724)

rankine        degF             The Rankine scale has the
           degreesrankine   Fahrenheit degree, but it's zero
           degF             is at absolute zero.
reaumur            10|8 degC  The Reaumur scale was used in Europe and

particularly in France. It is defined to be 0 at the freezing point of water and 80 at the boiling point. Reaumur apparently selected 80 because it is divisible by many numbers.

Units cannot handle wind chill or heat index because they are two variable
functions, but they are included here for your edification.  Clearly these
equations are the result of a model fitting operation.
wind chill index (WCI) a measurement of the combined cooling effect of low
     air temperature and wind on the human body. The index was first defined
     by the American Antarctic explorer Paul Siple in 1939. As currently used
     by U.S. meteorologists, the wind chill index is computed from the
     temperature T (in °F) and wind speed V (in mi/hr) using the formula:

WCI = 0.0817(3.71 sqrt(V) + 5.81 - 0.25V)(T - 91.4) + 91.4.

     For very low wind speeds, below 4 mi/hr, the WCI is actually higher than
     the air temperature, but for higher wind speeds it is lower than the air
     temperature.
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
     value from 0 to 1).

HI = -42.379 + 2.04901523 T + 1014.333127 H - 22.475541 TH - .00683783 T^2 - 548.1717 H^2 + 0.122874 T^2 H + 8.5282 T H^2 - 0.0199 T^2 H^2.

Physical constants
Basic constants
pi                    3.14159265358979323846
c                     2.99792458e8 m/s  speed of light in vacuum (exact)
light                 c
mu0                   4 pi 1e-7 H/m   permeability of vacuum (exact)
epsilon0              1/mu0 c^2       permittivity of vacuum (exact)
energy                c^2             convert mass to energy
e                    1.602176462e-19 C  electron charge
h                   6.62606876e-34 J s  Planck constant
hbar                  h / 2 pi
spin                  hbar
coulombconst          1/4 pi epsilon0  listed as "k" sometimes
Physico-chemical constants
atomicmassunit        1.66053873e-27 kg atomic mass unit (defined to be
u                     atomicmassunit    1|12 of the mass of carbon 12)
amu                   atomicmassunit
amu chem              1.66026e-27 kg  1|16 of the weighted average mass of

the 3 naturally occuring neutral

isotopes of oxygen

amu phys              1.65981e-27 kg  1|16 of the mass of a neutral

oxygen 16 atom

dalton                u               Maybe this should be amu_chem?
avogadro              grams/amu mol   size of a mole
N A                   avogadro
gasconstant         8.314472 J / mol K  molar gas constant
R                     gasconstant
boltzmann             R / N_A         Boltzmann constant
k                     boltzmann
molarvolume       mol R stdtemp / atm  Volume occupied by one mole of an

ideal gas at STP.

loschmidt   avogadro mol / molarvolume  Molecules per cubic meter of an

ideal gas at STP. Loschmidt did work similar to Avogadro.

stefanboltzmann pi^2 k^4 / 60 hbar^3 c^2  The power per area radiated by a
sigma                 stefanboltzmann   blackbody at temperature T is

given by sigma T^4.

wiendisplacement      2.8977686e-3 m K  Wien's Displacement Law gives the

frequency at which the Planck spectrum has maximum intensity. The relation is lambda T = b where lambda is wavelength, T is temperature and b is the Wien displacement. This relation is used to determine the temperature of stars.

K J  483597.9 GHz/V  Direct measurement of the volt is difficult.  Until

recently, laboratories kept Weston cadmium cells as a reference, but they could drift. In 1987 the CGPM officially recommended the use of the Josephson effect as a laboratory representation of the volt. The Josephson effect occurs when two superconductors are separated by a thin insulating layer. A "supercurrent" flows across the insulator with a frequency that depends on the potential applied across the superconductors. This frequency can be very accurately measured. The Josephson constant K_J, which is equal to 2e/h, relates the measured frequency to the potential. The value given here is the officially specified value for use beginning in 1990. The 1998 recommended value of the constant is 483597.898 GHz/V.

R K  25812.807 ohm   Measurement of the ohm also presents difficulties.

The old approach involved maintaining resistances that were subject to drift. The new standard is based on the Hall effect. When a current carrying ribbon is placed in a magnetic field, a potential difference develops across the ribbon. The ratio of the potential difference to the current is called the Hall resistance. Klaus von Klitzing discovered in 1980 that the Hall resistance varies in discrete jumps when the magnetic field is very large and the temperature very low. This enables accurate realization of the resistance h/e^2 in the lab. The value given here is the officially specified value for use beginning in 1990.

Various conventional values
Hg           13.5951 gram force / cm^3  Standard weight of mercury (exact)
water                 gram force/cm^3  Standard weight of water (exact)
waterdensity          gram / cm^3     Density of water
mach                  331.46 m/s      speed of sound in dry air at STP
Atomic constants
Rinfinity             10973731.568 /m  The wavelengths of a spectral series
R H                   10967760 /m       can be expressed as

1/lambda = R (1/m^2 - 1/n^2). where R is a number that various slightly from element to element. For hydrogen, R_H is the value, and for heavy elements, the value approaches Rinfinity, which can be computed from m_e c alpha^2 / 2 h with a loss of 5 digits of precision.

alpha                 7.297352533e-3  The fine structure constant was

introduced to explain fine structure visible in spectral lines. It can be computed from mu0 c e^2 / 2 h with a loss of 3 digits precision and loss of precision in derived values which use alpha.

bohrradius            alpha / 4 pi Rinfinity
prout                 185.5 keV       nuclear binding energy equal to 1|12

binding energy of the deuteron

Planck constants
planckmass            2.1767e-8 kg    sqrt(hbar c / G)
m P                   planckmass
plancktime            hbar / planckmass c^2
t P                   plancktime
plancklength          plancktime c
l P                   plancklength
Masses of elementary particles
electron          5.485799110e-4 u
proton            1.00727646688 u
neutron           1.00866491578 u
muon              0.1134289168 u
deuteron          2.01355321271 u
alpha particle     4.0015061747 u
particle wavelengths: the compton wavelength of a particle is
defined as h / m c where m is the mass of the particle.
Magnetic moments
bohrmagneton          e hbar / 2 electronmass
mu B                  bohrmagneton
nuclearmagneton       e hbar / 2 protonmass
mu N                  nuclearmagneton
Units derived from physical constants

kgf                   kg force
technicalatmosphere   kgf / cm^2
at                    technicalatmosphere
hyl                   kgf s^2 / m  Also gram-force s^2/m according to [15]
mmHg                  mm Hg
torr                  mmHg    These units, both named after Evangelista
tor                       Pa  Torricelli, should not be confused.
                              Acording to [15] the torr is actually
                              atm/760 which is slightly different.
inHg                  inch Hg
inH2O                 inch water
mmH2O                 mm water
eV                    e V     Energy acquired by a particle with charge e
electronvolt          eV        when it is accelerated through 1 V
lightyear             c julianyear  The 365.25 day year is specified in

NIST publication 811

lightsecond           c s
lightminute           c min
parsec                au / tan(arcsec)   Unit of length equal to distance
                  parsec               from the sun to a point having

heliocentric parallax of 1 arcsec (derived from parallax second). A distant object with paralax theta will be about (arcsec/theta) parsecs from the sun (using the approximation that tan(theta) = theta).

rydberg               h c Rinfinity      Rydberg energy
crith                 0.089885 gram      The crith is the mass of one

liter of hydrogen at standard temperature and pressure.

amagatvolume          molarvolume
amagat                mol/amagatvolume   Used to measure gas densities
lorentz               bohrmagneton / h c  Used to measure the extent
					       that the frequency of light

is shifted by a magnetic field.

cminv                 h c / cm           Unit of energy used in infrared
invcm                 cminv                spectroscopy.
wavenumber            cminv
kcal mol              kcal / mol N_A     kcal/mol is used as a unit of

energy by physical chemists.

CGS system based on centimeter, gram and second
dyne                  cm gram / s^2  force
dyn                   dyne
erg                   cm dyne        energy
poise                 gram / cm s    viscosity, honors Jean Poiseuille
P                     poise
rhe                   /poise         reciprocal viscosity
stokes                cm^2 / s       kinematic viscosity
St                    stokes
stoke                 stokes
lentor                stokes         old name
Gal                   cm / s^2       acceleration, used in geophysics
galileo               Gal            for earth's gravitational field
					 (note that "gal" is for gallon

but "Gal" is the standard symbol for the gal which is evidently a shortened form of "galileo".)

barye                 dyne/cm^2      pressure
barad                 barye          old name
kayser                1/cm           Proposed as a unit for wavenumber
balmer                kayser         Even less common name than "kayser"
kine                  cm/s           velocity
bole                  g cm / s       momentum
pond                  gram force
glug              gram force s^2 / cm  Mass which is accelerated at

1 cm/s^2 by 1 gram force

darcy         centipoise cm^2 / s atm  Measures permeability to fluid flow.

One darcy is the permeability of a medium that allows a flow of cc/s of a liquid of centipoise viscosity under a pressure gradient of atm/cm. Named for H. Darcy.

mohm                  cm / dyn s     mobile ohm, measure of mechanical
mobileohm             mohm             mobility
mechanicalohm         dyn s / cm     mechanical resistance
acousticalohm         dyn s / cm^5   ratio of the sound pressure of

1 dyn/cm^2 to a source of strength 1 cm^3/s

ray                   acousticalohm
rayl                  dyn s / cm^3   Specific acoustical resistance
eotvos                1e-9 Gal/cm    Change in gravitational acceleration

over horizontal distance

Electromagnetic units derived from the abampere
abampere              10 A           Current which produces a force of
abamp                 abampere         2 dyne/cm between two infinitely
aA                    abampere         long wires that are 1 cm apart
biot                  aA             alternative name for abamp
Bi                    biot
abcoulomb             abamp sec
abcoul                abcoulomb
abfarad               abampere sec / abvolt
abhenry               abvolt sec / abamp
abvolt                dyne cm / abamp sec
abohm                 abvolt / abamp
abmho                 /abohm
gauss                 abvolt sec / cm^2
Gs                    gauss
maxwell               abvolt sec     Also called the "line"
Mx                    maxwell
oersted               gauss / mu0
Oe                    oersted
gilbert               gauss cm / mu0
Gb                    gilbert
Gi                    gilbert
unitpole              4 pi maxwell
emu                   erg/gauss  "electro-magnetic unit", a measure of
				    magnetic moment, often used as emu/cm^3

to specify magnetic moment density.

Gaussian system: electromagnetic units derived from statampere.
Note that the Gaussian units are often used in such a way that Coulomb's law
has the form F= q1 * q2 / r^2.  The constant 1|4*pi*epsilon0 is incorporated
into the units.  From this, we can get the relation force=charge^2/dist^2.
This means that the simplification esu^2 = dyne cm^2 can be used to simplify
units in the Gaussian system, with the curious result that capacitance can be
measured in cm, resistance in sec/cm, and inductance in sec^2/cm.  These
units are given the names statfarad, statohm and stathenry below.
statampere            10 A cm / s c
statamp               statampere
statvolt              dyne cm / statamp sec
statcoulomb           statamp s
esu                   statcoulomb
statcoul              statcoulomb
statfarad             statamp sec / statvolt
cmcapacitance         statfarad
stathenry             statvolt sec / statamp
statohm               statvolt / statamp
statmho               /statohm
statmaxwell           statvolt sec
franklin              statcoulomb
debye                 1e-18 statcoul cm  unit of electrical dipole moment
helmholtz             debye/angstrom^2  Dipole moment per area
jar                   1000 statfarad   approx capacitance of Leyden jar
Some historical eletromagnetic units
intampere             0.999835 A   Defined as the current which in one
intamp                intampere      second deposits .001118 gram of

silver from an aqueous solution of silver nitrate.

intfarad              0.999505 F
intvolt               1.00033 V
intohm                1.000495 ohm  Defined as the resistance of a

uniform column of mercury containing 14.4521 gram in a column 1.063 m long and maintained at 0 degC.

daniell               1.042 V      Meant to be electromotive force of a

Daniell cell, but in error by .04 V

faraday               N_A e mol    Charge that must flow to deposit or
faraday phys          96521.9 C      liberate one gram equivalent of  any
faraday chem          96495.7 C      element.  (The chemical and physical

values are off slightly from what is obtained by multiplying by amu_chem or amu_phys. These values are from a 1991 NIST publication.) Note that there is a Faraday constant which is equal to N_A e and hence has units of C/mol.

kappline              6000 maxwell  Named by and for Gisbert Kapp
siemensunit           0.9534 ohm   Resistance of a meter long column of

mercury with a 1 mm cross section.

Photometric units
candle                1.02 candela  Standard unit for luminous  intensity
hefnerunit            0.9 candle     in use before candela
hefnercandle          hefnerunit
violle                20.17 cd     luminous intensity of 1 cm^2 of

platinum at its temperature of solidification (2045 K)

lumen                 cd sr        Luminous flux (luminous energy per
lm                    lumen           time unit)
talbot                lumen s      Luminous energy
lumberg               talbot
lux                   lm/m^2       Illuminance or exitance (luminous
lx                    lux            flux incident on or coming from
phot                  lumen / cm^2   a surface)
ph                    phot
footcandle            lumen/ft^2   Illuminance from a 1 candela source

at a distance of one foot

metercandle           lumen/m^2    Illuminance from a 1 candela source

at a distance of one meter

mcs                   metercandle s  luminous energy per area, used to

measure photographic exposure

nox                   1e-3 lux     These two units were proposed for
skot                  1e-3 apostilb  measurements relating to dark adapted

eyes.

Luminance measures
nit                   cd/m^2       Luminance: the intensity per projected
stilb                 cd / cm^2    area of an extended luminous source.
sb                    stilb        (nit is from latin nitere = to shine.)
apostilb              cd/pi m^2
asb                   apostilb
blondel               apostilb     Named after a French scientist.
Equivalent luminance measures.  These units are units which measure
the luminance of a surface with a specified exitance which obeys
Lambert's law.  (Lambert's law specifies that luminous intensity of
a perfectly diffuse luminous surface is proportional to the cosine
of the angle at which you view the luminous surface.)
equivalentlux         cd / pi m^2  luminance of a 1 lux surface
equivalentphot        cd / pi cm^2  luminance of a 1 phot surface
lambert               cd / pi cm^2
footlambert           cd / pi ft^2
The bril is used to express "brilliance" of a source of light on a
logarithmic scale to correspond to subjective perception.  An increase of 1
bril means doubling the luminance.  A luminance of 1 lambert is defined to
have a brilliance of 1 bril.
bril         bril(x) [;lambert] 2^(x+-100) lamberts  ;log2(bril/lambert)+100
Some luminance data from the IES Lighting Handbook, 8th ed, 1993
sunlum                1.6e9 cd/m^2  at zenith
sunillum              100e3 lux    clear sky
sunillum o            10e3 lux     overcast sky
sunlum h              6e6 cd/m^2   value at horizon
skylum                8000 cd/m^2  average, clear sky
skylum o              2000 cd/m^2  average, overcast sky
moonlum               2500 cd/m^2 
Photographic Exposure Value
The Additive Photographic EXposure (APEX) system developed in Germany in
the 1960s was an attempt to simplify exposure determination for people
who relied on exposure tables rather than exposure meters.  Shortly
thereafter, nearly all cameras incorporated exposure meters, so the APEX
system never caught on, but the concept of Exposure Value (EV) given by

A^2 LS ES

    2^EV = --- = -- = --

T K C

Where
    A = Relative aperture (f-number)
    T = Shutter time in seconds
    L = Scene luminance in cd/m2
    E = Scene illuminance in lux
    S = Arithmetic ISO film speed
    K = Reflected-light meter calibration constant
    C = Incident-light meter calibration constant
remains in use.  Strictly speaking, an Exposure Value is a combination
of aperture and shutter time, but it's also commonly used to indicate
luminance (or illuminance).  Conversion to luminance or illuminance
units depends on the ISO film speed and the meter calibration constant.
Common practice is to use an ISO film speed of 100 (because film speeds
are in even 1/3-step increments, the exact value is 64 * 2^(2|3)).
Calibration constants vary among camera and meter manufacturers: Canon,
Nikon, and Sekonic use a value of 12.5 for reflected-light meters, while
Minolta and Pentax use a value of 14.  Minolta and Sekonic use a value
of 250 for incident-light meters with flat receptors.
s100                  64 * 2^(2|3) / lx s    exact speed for ISO 100 film
                        
Reflected-light meter calibration constant with ISO 100 film
k1250                 12.5 (cd/m2) / lx s    For Canon, Nikon, and Sekonic
k1400                 14 (cd/m2) / lx s      For Minolta and Pentax
Incident-light meter calibration constant with ISO 100 film
c250                  250 lx / lx s          flat-disc receptor
Exposure value to scene luminance with ISO 100 film
For Minolta or Pentax

ev100(x) [;cd/m^2] 2^x k1400 / s100; log2(ev100 s100 / k1400)

For Canon, Nikon or Sekonic
ev100      ev100(x) [;cd/m^2] 2^x k1250 / s100; log2(ev100 s100 / k1250)
Exposure value to scene illuminance with ISO 100 film
iv100      iv100(x) [1;lx] 2^x c250 / s100; log2(iv100 s100 / c250)
Astronomical time measurements
Astronmical time measurement is a complicated matter.  The rotation of the
earth and motion of the planets is not uniform.  Originally the second was
defined relative to the "mean solar day".  It is necessary to use the mean
day because the earth's orbit is elliptical so the length of the day varies
throughout the year.  Simon Newcomb discovered that there were significant
irregularities in the rotation of the earth and he came up with equations
using the location of a fictitious mean sun.  The length of the second was
determined from the tropical year obtained from Newcomb's equations.  This
second was officially used from 1960 to 1967, at which point atomic clocks
replaced astronomical measurements for a standard of time.
The measures that appear below are probably obtained from an "ephemeris"
which is a set of equations that predicts the locations of the planets over
time.
anomalisticyear       365.2596 days      The time between successive

perihelion passages of the earth.

siderealyear          365.256360417 day  The time for the earth to make

one revolution around the sun relative to the stars.

tropicalyear          365.242198781 day  The mean interval between vernal

equinoxes. Differs from the sidereal year by 1 part in 26000 due to precession of the earth about its rotational axis combined with precession of the perihelion of the earth's orbit.

gaussianyear          365.2690 days      The orbital period of a body in

circular orbit at a distance of 1 au from the sun. Calculated from Kepler's third law.

elipseyear            346.62 days        The line of nodes is the

intersection of the plane of Earth's orbit around the sun with the plane of the moon's orbit around earth. Eclipses can only occur when the moon and sun are close to this line. The line rotates and appearances of the sun on the line of nodes occur every eclipse year.

saros                 223 synodicmonth   The earth, moon and sun appear in

the same arrangement every saros, so if an eclipse occurs, then one saros later, a similar eclipse will occur. (The saros is close to 19 eclipse years.) The eclipse will occur about 120 degrees west of the preceeding one because the saros is not an even number of days. After 3 saros, an eclipse will occur at approximately the same place.

siderealday           23.934469444 hour  The sidereal day is the interval
siderealhour          1|24 siderealday     between two successive transits
siderealminute        1|60 siderealhour    of a star over the meridian,
siderealsecond        1|60 siderealminute  or the time required  for the

earth to make one rotation relative to the stars. The more usual solar day is the time required to make a rotation relative to the sun. Because the earth moves in its orbit, it has to turn a bit extra to face the sun again, hence the solar day is slightly longer.

anomalisticmonth      27.55454977 day    Time for the moon to travel from

perigee to perigee

nodicalmonth          27.2122199 day     The nodes are the points where
draconicmonth         nodicalmonth         an orbit crosses the ecliptic.
draconiticmonth       nodicalmonth         This is the time required to

travel from the ascending node to the next ascending node.

siderealmonth         27.321661 day      Time required for the moon to

orbit the earth

lunarmonth            29 days+12 hours+44 minutes+2.8 seconds

Time between full moons. Full

synodicmonth          lunarmonth           moon occur when the sun and

lunation synodicmonth moon are on opposite sides of lune 1|30 lunation the earth. Since the earth lunour 1|24 lune moves around the sun, the moon has to revolve a bit farther to get into the full moon configuration. year tropicalyear yr year month 1|12 year mo month lustrum 5 years The Lustrum was a Roman purification ceremony that took place every five years. Classically educated Englishmen used this term. decade 10 years century 100 years millennium 1000 years millennia millennium solaryear year lunaryear 12 lunarmonth calendaryear 365 day commonyear 365 day leapyear 366 day julianyear 365.25 day gregorianyear 365.2425 day islamicyear 354 day A year of 12 lunar months. They islamicleapyear 355 day began counting on July 16, AD 622 when Muhammad emigrated to Medina (the year of the Hegira). They need 11 leap days in 30 years to stay in sync with the lunar year which is a bit longer than the 29.5 days of the average month. The months do not keep to the same seasons, but regress through the seasons every 32.5 years. islamicmonth 1|12 islamicyear They have 29 day and 30 day months.

The Hewbrew year is also based on lunar months, but synchronized to the solar
calendar.  The months vary irregularly between 29 and 30 days in length, and
the years likewise vary.  The regular year is 353, 354, or 355 days long.  To
keep up with the solar calendar, a leap month of 30 days is inserted every
3rd, 6th, 8th, 11th, 14th, 17th, and 19th years of a 19 year cycle.  This
gives leap years that last 383, 384, or 385 days.
The Hartree system of atomic units, derived from fundamental units
of mass (of electron), action (planck's constant), charge, and
the coulomb constant.
Fundamental units

atomicmass electronmass atomiccharge e atomicaction hbar

derived units (Warning: accuracy is lost from deriving them this way)

atomiclength bohrradius atomictime hbar^3/coulombconst^2 atomicmass e^4 Period of first bohr orbit atomicvelocity atomiclength / atomictime atomicenergy hbar / atomictime hartree atomicenergy Hartree hartree

These thermal units treat entropy as charge, from [5]

thermalcoulomb J/K entropy thermalampere W/K entropy flow thermalfarad J/K^2 thermalohm K^2/W thermal resistance fourier thermalohm thermalhenry J K^2/W^2 thermal inductance thermalvolt K thermal potential difference

United States units
linear measure
The US Metric Law of 1866 gave the exact relation 1 meter = 39.37 inches.
From 1893 until 1959, the foot was exactly 1200|3937 meters.  In 1959
the definition was changed to bring the US into agreement with other
countries.  Since then, the foot has been exactly 0.3048 meters.  At the
same time it was decided that any data expressed in feet derived from
geodetic surveys within the US would continue to use the old definition.

U.S. 1200|3937 m/ft These four values will convert US- US international measures to survey- US US Survey measures geodetic- US int 3937|1200 ft/m Convert US Survey measures to int- int international measures

inch 2.54 cm in inch foot 12 inch feet foot ft foot yard 3 ft yd yard mile 5280 ft The mile was enlarged from 5000 ft to this number in order to make it an even number of furlongs. (The Roman mile is 5000 romanfeet.) line 1|12 inch Also defined as '.1 in' or as '1e-8 Wb' rod (unit) 5.5 USyard perch rod furlong 40 rod From "furrow long" statutemile USmile league 3 USmile Intended to be an an hour's walk

surveyor's measure
surveyorschain        66 surveyft
surveyorspole         1|4 surveyorschain
surveyorslink         1|100 surveyorschain
chain                 surveyorschain
surveychain           chain
ch                    chain
link                  surveyorslink
acre                  10 chain^2
intacre               43560 ft^2  Acre based on international ft
acrefoot              acre surveyfoot
section               USmile^2
township              36 section
homestead             160 acre  Area of land granted by the 1862 Homestead

Act of the United States Congress

gunterschain          surveyorschain
engineerschain        100 ft
engineerslink         1|100 engineerschain
ramsdenschain         engineerschain
ramsdenslink          engineerslink
nautical measure
fathom                6 USft  Originally defined as the distance from

fingertip to fingertip with arms fully extended.

nauticalmile          1852 m  Supposed to be one minute of latitude at

the equator. That value is about 1855 m. Early estimates of the earth's circumference were a bit off. The value of 1852 m was made the international standard in 1929. The US did not accept this value until 1954. The UK switched in 1970.

cable                 1|10 nauticalmile
intcable              cable             international cable
cablelength           cable
UScable               100 fathom
navycablelength       720 USft          used for depth in water
marineleague          3 nauticalmile
geographicalmile      brnauticalmile
knot                  nauticalmile / hr
click                 km
Avoirdupois weight
pound                 0.45359237 kg  The one normally used
lb                    pound          From the latin libra
grain                 1|7000 pound   The grain is the same in all three
					 weight systems.  It was originally

defined as the weight of a barley corn taken from the middle of the ear.

ounce                 1|16 pound
oz                    ounce
dram                  1|16 ounce
dr                    dram
ushundredweight       100 pounds
cwt                   hundredweight
shorthundredweight    ushundredweight
uston                 shortton
shortton              2000 lb
quarterweight         1|4 uston
shortquarterweight    1|4 shortton
shortquarter          shortquarterweight
Troy Weight.  In 1828 the troy pound was made the first United States
standard weight.  It was to be used to regulate coinage.
troypound             5760 grain
troyounce             1|12 troypound
ozt                   troyounce
pennyweight           1|20 troyounce  Abbreviated "d" in reference to a
dwt                   pennyweight      Frankish coin called the "denier"

minted in the late 700's. There were 240 deniers to the pound.

assayton              mg ton / troyounce  mg / assayton = troyounce / ton
usassayton            mg uston / troyounce
brassayton            mg brton / troyounce
Some other jewelers units
metriccarat           0.2 gram       Defined in 1907
metricgrain           50 mg
carat                 metriccarat
ct                    carat
jewelerspoint         1|100 carat
silversmithpoint      1|4000 inch
Apothecaries' weight
appound               troypound
apounce               troyounce
apdram                1|8 apounce
apscruple             1|3 apdram
Liquid measure
gal                   gallon
quart                 1|4 gallon
pint                  1|2 quart
gill                  1|4 pint
usgallon              231 in^3
usquart               1|4 usgallon
uspint                1|2 usquart
usgill                1|4 uspint
usfluidounce          1|16 uspint
fluiddram             1|8 usfloz
minimvolume           1|60 fluiddram
qt                    quart
pt                    pint
floz                  fluidounce
usfloz                usfluidounce
fldr                  fluiddram
liquidbarrel          31.5 usgallon
usbeerbarrel          2 beerkegs
beerkeg               15.5 usgallon  Various among brewers
ponykeg               1|2 beerkeg
winekeg               12 usgallon
petroleumbarrel       42 usgallon    Originated in Pennsylvania oil
barrel                petroleumbarrel  fields, from the winetierce
bbl                   barrel
hogshead              2 liquidbarrel
usfirkin              9 gallon 
Dry measures: The Winchester Bushel was defined by William III in 1702 and
legally adopted in the US in 1836.
usbushel              2150.42 in^3  Volume of 8 inch cylinder with 18.5
bu                    bushel       inch diameter (rounded)
peck                  1|4 bushel
uspeck                1|4 usbushel
brpeck                1|4 brbushel
pk                    peck
drygallon             1|2 uspeck
dryquart              1|4 drygallon
drypint               1|2 dryquart
drybarrel             7056 in^3    Used in US for fruits, vegetables,
					 and other dry commodities except for

cranberries.

cranberrybarrel       5826 in^3    US cranberry barrel
heapedbushel          1.278 usbushel Why this particular value? Often
					 rounded to 1.25 bushels.
Grain measures.  The bushel as it is used by farmers in the USA is actually
a measure of mass which varies for different commodities.  Canada uses the
same bushel masses for most commodities, but not for oats.
wheatbushel           60 lb
soybeanbushel         60 lb
cornbushel            56 lb
ryebushel             56 lb
barleybushel          48 lb
oatbushel             32 lb
ricebushel            45 lb
canada oatbushel      34 lb
Wine and Spirits measure
ponyvolume            1 usfloz
jigger                1.5 usfloz  Can vary between 1 and 2 usfloz
shot                  jigger    Sometimes 1 usfloz
eushot                25 ml     EU standard spirits measure
fifth                 1|5 usgallon
winebottle            750 ml    US industry standard, 1979
winesplit             1|4 winebottle
wineglass             4 usfloz
magnum                1.5 liter  Standardized in 1979, but given
				    as 2 qt in some references
metrictenth           375 ml
metricfifth           750 ml
metricquart           1 liter 
French champagne bottle sizes
split                 200 ml
jeroboam              2 magnum
rehoboam              3 magnum
methuselah            4 magnum
salmanazar            6 magnum
balthazar             8 magnum
nebuchadnezzar        10 magnum 
Water is "hard" if it contains various minerals, expecially calcium
carbonate.
clarkdegree   1|70000      Content by weigh of calcium carbonate
gpg           grains/gallon  Divide by water's density to convert to

a dimensionless concentration measure

Shoe measures
shoeiron              1|48 inch   Used to measure leather in soles
shoeounce             1|64 inch   Used to measure non-sole shoe leather
USA shoe sizes.  These express the length of the shoe or the length
of the "last", the form that the shoe is made on.
shoesize delta        1|3 inch    USA shoe sizes differ by this amount
shoe men0             8.25 inch
shoe women0           (7+11|12) inch
shoe boys0            (3+11|12) inch
shoe girls0           (3+7|12) inch
European shoe size.  According to
     http://www.shoeline.com/footnotes/shoeterm.shtmlparis points
sizes in Europe are measured with Paris points which simply measure
the length of the shoe.
europeshoesize        2|3 cm
USA slang units
buck                  US$
fin                   5 US$
sawbuck               10 US$
grand                 1000 US$
greenback             US$
key                   kg          usually of marijuana, 60's
lid                   1 oz        Another 60's weed unit
footballfield         100 yards
marathon              26 miles + 385 yards
British
UK                    1200000|3937014 m/ft  The UK lengths were defined by
british-                UK                     a bronze bar manufactured in
UK-                     UK                     1844.  Measurement of that bar

revealed the dimensions given here.

brnauticalmile        6080 ft              Used until 1970 when the UK
brknot                brnauticalmile / hr  switched to the international
brcable               1|10 brnauticalmile  nautical mile.
admiraltymile         brnauticalmile
admiraltyknot         brknot
admiraltycable        brcable
seamile               6000 ft
shackle               15 fathoms           Adopted 1949 by British navy
British Imperial weight is mostly the same as US weight.  A few extra
units are added here.
clove                 7 lb  
stone                 14 lb
tod                   28 lb
brquarterweight       1|4 brhundredweight
brhundredweight       8 stone
longhundredweight     brhundredweight
long ton              20 brhundredweight
brton                 long_ton
British Imperial volume measures
brminim               1|60 brdram
brscruple             1|3 brdram
fluidscruple          brscruple
brdram                1|8 brfloz
brfluidounce          1|20 brpint
brfloz                brfluidounce
brgill                1|4 brpint
brpint                1|2 brquart
brquart               1|4 brgallon
brgallon              4.54609 l     The British Imperial gallon was
					defined in 1824 to be the volume of

water which weighed 10 pounds at 62 deg F with a pressure of 30 inHg. In 1963 it was defined to be the volume occupied by 10 pounds of distilled water of density 0.998859 g/ml weighed in air of density 0.001217 g/ml against weights of density 8.136 g/ml. This gives a value of approximately 4.5459645 liters, but the old liter was in force at this time. In 1976 the definition was changed to exactly 4.54609 liters using the new definition of the liter (1 dm^3).

brbarrel              36 brgallon   Used for beer
brbushel              8 brgallon
brheapedbushel        1.278 brbushel
brquarter             8 brbushel
brchaldron            36 brbushel
Units derived from imperial system
ouncedal              oz ft / s^2    force which accelerates an ounce

at 1 ft/s^2

poundal               lb ft / s^2    same thing for a pound
tondal                ton ft / s^2   and for a ton
pdl                   poundal
psi                   pound force / inch^2
psia                  psi            absolute pressure
tsi                   ton force / inch^2
reyn                  psi sec
slug                  lbf s^2 / ft
slugf                 slug force
slinch                lbf s^2 / inch  Mass unit derived from inch second
slinchf               slinch force     pound-force system.  Used in space

applications where in/sec^2 was a natural acceleration measure.

geepound              slug
lbf                   lb force
tonf                  ton force
lbm                   lb
kip                   1000 lbf    from kilopound
ksi                   kip / in^2
mil                   0.001 inch
thou                  0.001 inch
circularinch          1|4 pi in^2  area of a one-inch diameter circle
circularmil           1|4 pi mil^2  area of one-mil diameter circle
cmil                  circularmil
cental                100 pound
centner               cental
caliber               0.01 inch   for measuring bullets
duty                  ft lbf
celo                  ft / s^2
jerk                  ft / s^3
australiapoint        0.01 inch   The "point" is used to measure rainfall

in Australia

sabin                 ft^2        Measure of sound absorption equal to the

absorbing power of one square foot of a perfectly absorbing material. The sound absorptivity of an object is the area times a dimensionless absorptivity coefficient.

standardgauge        4 ft + 8.5 in  Standard width between railroad track
flag                 5 ft^2       Construction term referring to sidewalk.
rollwallpaper        30 ft^2      Area of roll of wall paper
fillpower            in^3 / ounce  Density of down at standard pressure.
					The best down has 750-800 fillpower.
pinlength            1|16 inch    A 17 pin is 17/16 in long in the USA.
buttonline           1|40 inch    The line was used in 19th century USA

to measure width of buttons.

scoopnumber          /quart       Ice cream scoops are labeled with a

number specifying how many scoops fill a quart.

beespace             1|4 inch     Bees will fill any space that is smaller

than the bee space and leave open spaces that are larger. The size of the space varies with species.

diamond              8|5 ft       Marking on US tape measures that is

useful to carpenters who wish to place five studs in an 8 ft distance. Note that the numbers appear in red every 16 inches as well, giving six divisions in 8 feet.

retmaunit            1.75 in      Height of rack mountable equipment.
U                    retmaunit      Equipment should be 1|32 inch narrower

than its U measurement indicates to allow for clearance, so 4U=(6+31|32)in

Other units of work, energy, power, etc
Calories: energy to raise a gram of water one degree celsius
cal IT                4.1868 J    International Table calorie
cal th                4.184 J     Thermochemical calorie
cal fifteen           4.18580 J   Energy to go from 14.5 to 15.5 degC
cal twenty            4.18190 J   Energy to go from 19.5 to 20.5 degC
cal mean              4.19002 J   1|100 energy to go from 0 to 100 degC
calorie               cal_IT
cal                   calorie
calorie IT            cal_IT
thermcalorie          cal_th
calorie th            thermcalorie
Calorie               kilocalorie  the food Calorie
thermie            1e6 cal_fifteen  Heat required to raise the

temperature of a tonne of water from 14.5 to 15.5 degC.

btu definitions: energy to raise a pound of water 1 degF
btu                   cal lb degF / gram K  international table BTU
britishthermalunit    btu
btu IT                btu
btu th                cal_th lb degF / gram K
btu mean              cal_mean lb degF / gram K
quad                  quadrillion btu
ECtherm               1.05506e8 J   Exact definition, close to 1e5 btu
UStherm               1.054804e8 J  Exact definition
therm                 UStherm
toe                   1e10 cal_IT   ton oil equivalent.  Energy released

by burning one metric ton of oil. [18]

tonscoal              1|2.3 toe     Energy in metric ton coal from [18].
naturalgas            toe / 1270 m^3  Energy released from natural gas

from [18]. (At what pressure?)

Celsius heat unit: energy to raise a pound of water 1 degC
celsiusheatunit       cal lb degC / gram K
chu                   celsiusheatunit
The horsepower is supposedly the power of one horse pulling.   Obviously
different people had different horses.
ushorsepower          550 foot pound force / sec  Invented by James Watt
hp                    horsepower
metrichorsepower      75 kilogram force meter / sec
electrichorsepower    746 W
boilerhorsepower      9809.50 W
waterhorsepower       746.043 W
brhorsepower          745.70 W
donkeypower           250 W
Thermal insulance: Thermal conductivity has dimension power per area per
(temperature difference per length thickness) which comes out to W / K m.  If
the thickness is fixed, then the conductance will have units of W / K m^2.
Thermal insulance is the reciprocal.
Rvalue                degF ft^2 hr / btu
Uvalue                1/Rvalue
europeanUvalue        watt / m^2 K
RSI                   degC m^2 / W
clo                   0.155 degC m^2 / W  Supposed to be the insulance

required to keep a resting person comfortable indoors. The value given is from NIST and the CRC, but [5] gives a slightly different value of 0.875 ft^2 degF hr / btu.

tog                   0.1 degC m^2 / W  Also used for clothing.
Misc other measures
ENTROPY                 ENERGY / TEMPERATURE
clausius              1e3 cal/K      A unit of physical entropy
langley               thermcalorie/cm^2   Used in radiation theory
poncelet              100 kg force m / s
tonrefrigeration      ton 144 btu / lb day  One ton refrigeration is

the rate of heat extraction required turn one ton of water to ice in a day. Ice is defined to have a latent heat of 144 btu/lb.

tonref                tonrefrigeration
refrigeration         tonref / ton
frigorie              1000 cal_fifteen Used in refrigeration engineering.
tnt                   1e9 cal_th / ton So you can write tons-tnt. This

is a defined, not measured, value.

airwatt               8.5 (ft^3/min) inH2O  Measure of vacuum power as

pressure times air flow.

Permeability: The permeability or permeance, n, of a substance determines
how fast vapor flows through the substance.  The formula W = n A dP
holds where W is the rate of flow (in mass/time), n is the permeability,
A is the area of the flow path, and dP is the vapor pressure difference.
perm 0C               grain / hr ft^2 inHg
perm zero             perm_0C
perm 0                perm_0C
perm                  perm_0C
perm 23C              grain / hr ft^2 in Hg23C
perm twentythree      perm_23C
Counting measures
pair                  2
brace (grouping))     2
nest                  3    often used for items like bowls that
				 nest together
hattrick              3    Used in sports, especially cricket and ice

hockey to report the number of goals.

dicker                10
dozen                 12
bakersdozen           13
score                 20
flock                 40
timer                 40
shock                 60
gross                 144
greatgross            12 gross
tithe                 1|10  From Anglo-Saxon word for tenth
Paper counting measure
shortquire            24
quire                 25
shortream             480
ream                  500
perfectream           516
bundle                2 reams
bale                  5 bundles
Paper measures
pointthickness        mil
The metric paper sizes are defined so that if a sheet is cut in half
along the short direction, the result is two sheets which are
similar to the original sheet.  This means that for any metric size,
the long side is close to sqrt(2) times the length of the short
side.  Each series of sizes is generated by repeated cuts in half,
with the values rounded down to the nearest millimeter.
A6paper               105 mm 148 mm
A7paper                74 mm 105 mm
A8paper                52 mm 74 mm
A9paper                37 mm 52 mm
A10paper               26 mm 37 mm
B0paper              1000 mm 1414 mm  The basic B size has an area
B1paper               707 mm 1000 mm  of sqrt(2) square meters.
B2paper               500 mm 707 mm
B3paper               353 mm 500 mm
B4paper               250 mm 353 mm
B5paper               176 mm 250 mm
B6paper               125 mm 176 mm
B7paper                88 mm 125 mm
B8paper                62 mm 88 mm
B9paper                44 mm 62 mm
B10paper               31 mm 44 mm
C0paper               917 mm 1297 mm  The basic C size has an area
C1paper               648 mm 917 mm   of sqrt(sqrt(2)) square meters.
C2paper               458 mm 648 mm
C3paper               324 mm 458 mm   Intended for envelope sizes
C4paper               229 mm 324 mm
C5paper               162 mm 229 mm
C6paper               114 mm 162 mm
C7paper                81 mm 114 mm
C8paper                57 mm 81 mm
C9paper                40 mm 57 mm
C10paper               28 mm 40 mm 
gsm (Grams per Square Meter), a sane, metric paper weight measure
gsm                   grams / meter^2
In the USA, a collection of crazy historical paper measures are used.  Paper
is measured as a weight of a ream of that particular type of paper.  This is
sometimes called the "substance" or "basis" (as in "substance 20" paper).
The standard sheet size or "basis size" varies depending on the type of
paper.  As a result, 20 pound bond paper and 50 pound text paper are actually
about the same weight.  The different sheet sizes were historically the most
convenient for printing or folding in the different applications.  These
different basis weights are standards maintained by American Society for
Testing Materials (ASTM) and the American Forest and Paper Association
(AF&PA).
poundbookpaper        lb / 25 inch 38 inch ream
lbbook                poundbookpaper
poundtextpaper        poundbookpaper
lbtext                poundtextpaper
poundoffsetpaper      poundbookpaper   For offset printing
lboffset              poundoffsetpaper
poundbiblepaper       poundbookpaper   Designed to be lightweight, thin,
lbbible               poundbiblepaper  strong and opaque.
poundtagpaper         lb / 24 inch 36 inch ream
lbtag                 poundtagpaper
poundbagpaper         poundtagpaper
lbbag                 poundbagpaper
poundnewsprintpaper   poundtagpaper
lbnewsprint           poundnewsprintpaper
poundposterpaper      poundtagpaper
lbposter              poundposterpaper
poundtissuepaper      poundtagpaper
lbtissue              poundtissuepaper
poundwrappingpaper    poundtagpaper
lbwrapping            poundwrappingpaper
poundwaxingpaper      poundtagpaper
lbwaxing              poundwaxingpaper
poundglassinepaper    poundtagpaper
lbglassine            poundglassinepaper
poundcoverpaper       lb / 20 inch 26 inch ream
lbcover               poundcoverpaper
poundindexpaper       lb / 25.5 inch 30.5 inch ream
lbindex               poundindexpaper
poundbondpaper        lb / 17 inch 22 inch ream  Bond paper is stiff and
lbbond                poundbondpaper            durable for repeated
poundwritingpaper     poundbondpaper            filing, and it resists
lbwriting             poundwritingpaper         ink penetration.
poundledgerpaper      poundbondpaper
lbledger              poundledgerpaper
poundcopypaper        poundbondpaper
lbcopy                poundcopypaper
poundblottingpaper    lb / 19 inch 24 inch ream
lbblotting            poundblottingpaper
poundblankspaper      lb / 22 inch 28 inch ream
lbblanks              poundblankspaper
poundpostcardpaper    lb / 22.5 inch 28.5 inch ream
lbpostcard            poundpostcardpaper
poundweddingbristol   poundpostcardpaper
lbweddingbristol      poundweddingbristol
poundbristolpaper     poundweddingbristol
lbbristol             poundbristolpaper
poundboxboard         lb / 1000 ft^2
lbboxboard            poundboxboard
poundpaperboard       poundboxboard
lbpaperboard          poundpaperboard 
When paper is marked in units of M, it means the weight of 1000 sheets of the
given size of paper.  To convert this to paper weight, divide by the size of
the paper in question.
paperM                lb / 1000
Printing
fournierpoint         0.1648 inch / 12  First definition of the printers

point made by Pierre Fournier who defined it in 1737 as 1|12 of a cicero which was 0.1648 inches.

olddidotpoint         1|72 frenchinch  François Ambroise Didot, one of

a family of printers, changed Fournier's definition around 1770 to fit to the French units then in use.

bertholdpoint         1|2660 m         H. Berthold tried to create a

metric version of the didot point in 1878.

INpoint               0.4 mm           This point was created by a

group directed by Fermin Didot in 1881 and is associated with the imprimerie nationale. It doesn't seem to have been used much.

germandidotpoint      0.376065 mm      Exact definition appears in DIN

16507, a German standards document of 1954. Adopted more broadly in 1966 by ???

metricpoint           3|8 mm           Proposed in 1977 by Eurograf
point                 1|72.27 inch     The American point was invented
printerspoint         point            by Nelson Hawks in 1879 and

dominates USA publishing. It was standardized by the American Typefounders Association at the value of 0.013837 inches exactly. Knuth uses the approximation given here (which is very close). The comp.fonts FAQ claims that this value is supposed to be 1|12 of a pica where 83 picas is equal to 35 cm. But this value differs from the standard.

texscaledpoint        1|65536 point    The TeX typesetting system uses
texsp                 texscaledpoint   this for all computations.
computerpoint         1|72 inch        The American point was rounded
computerpica          12 computerpoint  to an even 1|72 inch by computer
postscriptpoint       computerpoint    people at some point.
pspoint               postscriptpoint
Q                     1|4 mm           Used in Japanese phototypesetting

Q is for quarter

frenchprinterspoint   olddidotpoint
didotpoint            germandidotpoint  This seems to be the dominant value
europeanpoint         didotpoint       for the point used in Europe
cicero                12 didotpoint
stick                 2 inches
Type sizes
excelsior             3 point
brilliant             3.5 point
diamondtype           4 point
pearl                 5 point
agate                 5.5 point  Originally agate type was 14 lines per
				      inch, giving a value of 1|14 in.
ruby                  agate     British
nonpareil             6 point
mignonette            6.5 point
emerald               mignonette  British
minion                7 point
brevier               8 point
bourgeois             9 point
longprimer            10 point
smallpica             11 point
pica                  12 point
english       14 point
columbian             16 point
greatprimer           18 point
paragon               20 point
meridian              44 point
canon                 48 point
German type sizes
nonplusultra          2 didotpoint
brillant              3 didotpoint
diamant               4 didotpoint
perl                  5 didotpoint
nonpareille           6 didotpoint
kolonel               7 didotpoint
petit                 8 didotpoint
borgis                9 didotpoint
korpus                10 didotpoint
corpus                korpus
garamond              korpus
mittel                14 didotpoint
tertia                16 didotpoint
text                  18 didotpoint
kleine kanon          32 didotpoint
kanon                 36 didotpoint
grobe kanon           42 didotpoint
missal                48 didotpoint
kleine sabon          72 didotpoint
grobe sabon           84 didotpoint 
Information theory units.  Note that the name "entropy" is used both
to measure information and as a physical quantity.
nat                   ln(2) bits          Entropy measured base e
hartley               log2(10) bits       Entropy of a uniformly

distributed random variable over 10 symbols.

Computer
bps                   bit/sec             Sometimes the term "baud" is

incorrectly used to refer to bits per second. Baud refers to symbols per second. Modern modems transmit several bits per symbol.

byte                  8 bit               Not all machines had 8 bit
B                     byte                  bytes, but these days most of

them do. But beware: for transmission over modems, a few extra bits are used so there are actually 10 bits per byte.

nybble                4 bits              Half of a byte. Sometimes

equal to different lengths such as 3 bits.

nibble                nybble
meg                   megabyte            Some people consider these

units along with the kilobyte

gig                   gigabyte            to be defined according to

powers of 2 with the kilobyte equal to 2^10 bytes, the megabyte equal to 2^20 bytes and the gigabyte equal to 2^30 bytes but these usages are forbidden by SI. Binary prefixes have been defined by IEC to replace the SI prefixes. Use them to get the binary values: KiB, MiB, and GiB.

jiffy                 0.01 sec    This is defined in the Jargon File
jiffies               jiffy       (http://www.jargon.org) as being the

duration of a clock tick for measuring wall-clock time. Supposedly the value used to be 1|60 sec or 1|50 sec depending on the frequency of AC power, but then 1|100 sec became more common. On linux systems, this term is used and for the Intel based chips, it does have the value of .01 sec. The Jargon File also lists two other definitions: millisecond, and the time taken for light to travel one foot.

Musical measures.  Musical intervals expressed as ratios.  Multiply
two intervals together to get the sum of the interval.  The function
musicalcent can be used to convert ratios to cents.
Perfect intervals
octave                2
majorsecond           musicalfifth^2 / octave
majorthird            5|4
minorthird            6|5
musicalfourth         4|3
musicalfifth          3|2
majorsixth            musicalfourth majorthird
minorsixth            musicalfourth minorthird
majorseventh          musicalfifth majorthird
minorseventh          musicalfifth minorthird 
pythagoreanthird      majorsecond musicalfifth^2 / octave
syntoniccomma         pythagoreanthird / majorthird
pythagoreancomma      musicalfifth^12 / octave^7
Equal tempered definitions
semitone              octave^(1|12)
musicalcent  (x) [1;1]   semitone^(x/100) ; 100 log(musicalcent)/log(semitone) 
Musical note lengths.
wholenote             !
halfnote              1|2 wholenote
quarternote           1|4 wholenote
eighthnote            1|8 wholenote
sixteenthnote         1|16 wholenote
thirtysecondnote      1|32 wholenote
sixtyfourthnote       1|64 wholenote
dotted                3|2
doubledotted          7|4
breve                 doublewholenote
semibreve             wholenote
minimnote             halfnote
crochet               quarternote
quaver                eighthnote
semiquaver            sixteenthnote
demisemiquaver        thirtysecondnote
hemidemisemiquaver    sixtyfourthnote
semidemisemiquaver    hemidemisemiquaver
yarn and cloth measures
yarn linear density
woolyarnrun           1600 yard/pound  1600 yds of "number 1 yarn" weighs

a pound.

yarncut               300 yard/pound  Less common system used in

Pennsylvania for wool yarn

cottonyarncount       840 yard/pound
linenyarncount        300 yard/pound  Also used for hemp and ramie
worstedyarncount      1680 ft/pound
metricyarncount       meter/gram
denier                1|9 tex           used for silk and rayon
manchesteryarnnumber  drams/1000 yards  old system used for silk
pli                   lb/in
typp                  1000 yd/lb
asbestoscut           100 yd/lb   used for glass and asbestos yarn
tex                   gram / km   rational metric yarn measure, meant
drex                  0.1 tex     to be used for any kind of yarn
poumar                lb / 1e6 yard
yarn and cloth length
skeincotton           80*54 inch  80 turns of thread on a reel with a
				       54 in circumference (varies for other

kinds of thread)

cottonbolt            120 ft      cloth measurement
woolbolt              210 ft 
bolt                  cottonbolt
heer                  600 yards
cut                   300 yards   used for wet-spun linen yarn
lea                   300 yards
drug dosage
mcg                   microgram       Frequently used for vitamins
iudiptheria           62.8 microgram  IU is for international unit
iupenicillin          0.6 microgram
iuinsulin             41.67 microgram
drop                  1|20 ml         The drop was an old "unit" that was

replaced by the minim. But I was told by a pharmacist that in his profession, the conversion of 20 drops per ml is actually used.

bloodunit             450 ml          For whole blood.  For blood

components, a blood unit is the quanity of the component found in a blood unit of whole blood. The human body contains about 12 blood units of whole blood.

fixup units for times when prefix handling doesn't do the job
hectare               hectoare
megohm                megaohm
kilohm                kiloohm
microhm               microohm
megalerg              megaerg   'L' added to make it pronounceable [18]. 
olddollargold         23.22 grains goldprice  Used until 1934
newdollargold         96|7 grains goldprice  After Jan 31, 1934
dollargold            newdollargold
poundgold             113 grains goldprice
Nominal masses of US coins.  Note that dimes, quarters and half dollars
have weight proportional to value.  Before 1965 it was $40 / kg.
USpennyweight         2.5 grams        Since 1982, 48 grains before
USnickelweight        5 grams
USdimeweight          10 cents / (20 US$ / lb)  Since 1965
USquarterweight       25 cents / (20 US$ / lb)  Since 1965
UShalfdollarweight    50 cents / (20 US$ / lb)  Since 1971
USdollarmass          8.1 grams
British currency
quid                  britainpound       Slang names
fiver                 5 quid
tenner                10 quid
shilling              1|20 britainpound  Before decimalisation, there
oldpence              1|12 shilling      were 20 shillings to a pound,
farthing              1|4 oldpence       each of twelve old pence
crown                 5 shilling
brpenny               0.01 britainpound
pence                 penny
tuppence              2 pence
tuppenny              tuppence
oldpenny              oldpence
oldtuppence           2 oldpence
oldtuppenny           oldtuppence
threepence            3 oldpence   threepence never refers to new money
threepenny            threepence
oldthreepence         threepence
oldthreepenny         threepence
oldhalfpenny          halfoldpenny
oldhapenny            oldha'penny
brpony                25 britainpound
Canadian currency
loony                 1 canadadollar   This coin depicts a loon
toony                 2 canadadollar
Oceanographic flow
sverdrup              1e6 m^3 / sec  Used to express flow of ocean

currents. Named after Norwegian oceanographer H. Sverdrup.

In vacuum science and some other applications, gas flow is measured
as the product of volumetric flow and pressure.  This is useful
because it makes it easy to compare with the flow at standard
pressure (one atmosphere).  It also directly relates to the number
of gas molecules per unit time, and hence to the mass flow if the
molecular mass is known.
sccm                  atm cc/min    's' is for "standard" to indicate
sccs                  atm cc/sec    flow at standard pressure
scfh                  atm ft^3/hour
scfm                  atm ft^3/min
slpm                  atm liter/min
slph                  atm liter/hour
lusec                 liter micron Hg / s  Used in vacuum science 
Wire Gauge
This area is a nightmare with huge charts of wire gauge diameters
that usually have no clear origin.  There are at least 5 competing wire gauge
systems to add to the confusion.  The use of wire gauge is related to the
manufacturing method: a metal rod is heated and drawn through a hole.  The
size change can't be too big.  To get smaller wires, the process is repeated
with a series of smaller holes.  Generally larger gauges mean smaller wires.
The gauges often have values such as "00" and "000" which are larger sizes
than simply "0" gauge.  In the tables that appear below, these gauges must be
specified as negative numbers (e.g. "00" is -1, "000" is -2, etc).
Alternatively, you can use the following units:
g00                    (-1)
g000                   (-2)
g0000                  (-3)
g00000                 (-4)
g000000                (-5)
g0000000               (-6)
American Wire Gauge (AWG) or Brown & Sharpe Gauge appears to be the most
important gauge. ASTM B-258 specifies that this gauge is based on geometric
interpolation between gauge 0000, which is 0.46 inches exactly, and gauge 36
which is 0.005 inches exactly.  Therefore, the diameter in inches of a wire
is given by the formula 1|200 92^((36-g)/39).  Note that 92^(1/39) is close
to 2^(1/6), so diameter is approximately halved for every 6 gauges.  For the
repeated zero values, use negative numbers in the formula.  The same document
also specifies rounding rules which seem to be ignored by makers of tables.
Gauges up to 44 are to be specified with up to 4 significant figures, but no
closer than 0.0001 inch.  Gauges from 44 to 56 are to be rounded to the
nearest 0.00001 inch.
In addition to being used to measure wire thickness, this gauge is used to
measure the thickness of sheets of aluminum, copper, and most metals other
than steel, iron and zinc.
wiregauge(g) [;m] 1|200 92^((36+(-g))/39) in;36+(-39)ln(200 wiregauge/in)/ln(92)
Next we have the SWG, the Imperial or British Standard Wire Gauge.  This one
is piecewise linear.  It was used for aluminum sheets.
The following is from the Appendix to ASTM B 258
   For example, in U.S. gage, the standard for sheet metal is based on the
   weight of the metal, not on the thickness. 16-gage is listed as
   approximately .0625 inch thick and 40 ounces per square foot (the original
   standard was based on wrought iron at .2778 pounds per cubic inch; steel
   has almost entirely superseded wrought iron for sheet use, at .2833 pounds
   per cubic inch). Smaller numbers refer to greater thickness. There is no
   formula for converting gage to thickness or weight.
It's rather unclear from the passage above whether the plate gauge values are
therefore wrong if steel is being used.  Reference [15] states that steel is
in fact measured using this gauge (under the name Manufacturers' Standard
Gauge) with a density of 501.84 lb/ft3 = 0.2904 lb/in3 used for steel.
But this doesn't seem to be the correct density of steel (.2833 lb/in3 is
closer).
This gauge was established in 1893 for purposes of taxation.
Old plate gauge for iron
Manufacturers Standard Gage
A special gauge is used for zinc sheet metal.  Notice that larger gauges
indicate thicker sheets.
Screw sizes
In the USA, screw diameters are reported using a gauge number.
Metric screws are reported as Mxx where xx is the diameter in mm.
Ring size. All ring sizes are given as the circumference of the ring.
USA ring sizes.  Several slightly different definitions seem to be in
circulation.  According to [15], the interior diameter of size n ring in
inches is 0.32 n + 0.458 for n ranging from 3 to 13.5 by steps of 0.5.  The
size 2 ring is inconsistently 0.538in and no 2.5 size is listed.
However, other sources list 0.455 + 0.0326 n and 0.4525 + 0.0324 n as the
diameter and list no special case for size 2.  (Or alternatively they are
1.43 + .102 n and 1.4216+.1018 n for measuring circumference in inches.)  One
reference claimed that the original system was that each size was 1|10 inch
circumference, but that source doesn't have an explanation for the modern
system which is somewhat different.
Old practice in the UK measured rings using the "Wheatsheaf gauge" with sizes
specified alphabetically and based on the ring inside diameter in steps of
1|64 inch.  This system was replaced in 1987 by British Standard 6820 which
specifies sizes based on circumference.  Each size is 1.25 mm different from
the preceding size.  The baseline is size C which is 40 mm circumference.
The new sizes are close to the old ones.  Sometimes it's necessary to go
beyond size Z to Z+1, Z+2, etc.
Japanese sizes start with size 1 at a 13mm inside diameter and each size is
1|3 mm larger in diameter than the previous one.  They are multiplied by pi
to give circumference.
The European ring sizes are the length of the circumference in mm minus 40.
Abbreviations
mph                   mile/hr
mpg                   mile/gal
kph                   km/hr
fL                    footlambert
fpm                   ft/min
fps                   ft/s
rpm                   rev/min
rps                   rev/sec
mi                    mile
mbh                   1e3 btu/hour
mcm                   1e3 circularmil
ipy                   inch/year   used for corrosion rates
ccf                   100 ft^3    used for selling water [18]
Mcf                   1000 ft^3   not million cubic feet [18]
kp                    kilopond
kpm                   kp meter
kWh                   kW hour
hph                   hp hour
Radioactivity units
becquerel             /s          Activity of radioactive source
Bq                    becquerel
curie                 3.7e10 Bq   Defined in 1910 as the radioactivity
Ci                    curie       emitted by the amount of radon that is

in equilibrium with 1 gram of radium.

rutherford            1e6 Bq
gray                  J/kg        Absorbed dose of radiation
Gy                    gray
rad                   1e-2 Gy     From Radiation Absorbed Dose
rep                   8.38 mGy    Roentgen Equivalent Physical, the amount

of radiation which , absorbed in the body, would liberate the same amount of energy as 1 roentgen of X rays would, or 97 ergs.

sievert               J/kg        Dose equivalent:  dosage that has the
Sv                    sievert       same effect on human tissues as 200
rem                   1e-2 Sv       keV X-rays.  Different types of

radiation are weighted by the Relative Biological Effectiveness (RBE).

Radiation type RBE X-ray, gamma ray 1 beta rays, > 1 MeV 1 beta rays, < 1 MeV 1.08 neutrons, < 1 MeV 4-5 neutrons, 1-10 MeV 10 protons, 1 MeV 8.5 protons, .1 MeV 10 alpha, 5 MeV 15 alpha, 1 MeV 20

The energies are the kinetic energy of the particles. Slower particles interact more, so they are more effective ionizers, and hence have higher RBE values.

rem stands for Roentgen Equivalent Mammal

roentgen            2.58e-4 C / kg  Ionizing radiation that produces

1 statcoulomb of charge in 1 cc of dry air at stp.

rontgen               roentgen    Sometimes it appears spelled this way
sievertunit           8.38 rontgen  Unit of gamma ray dose delivered in one

hour at a distance of 1 cm from a point source of 1 mg of radium enclosed in platinum .5 mm thick.

eman                  1e-7 Ci/m^3  radioactive concentration
mache                 3.7e-7 Ci/m^3
A few German units as currently in use.
zentner               50 kg
doppelzentner         2 zentner
pfund                 500 g
Some definitions using ISO 8859-1 characters
¢                     cent
£                     britainpound
¥                     japanyen
ångström              angstrom
Å                     angstrom
röntgen               roentgen
The following units were in the unix units database but do not appear in
this file:
   wey      used for cheese, salt and other goods.  Measured mass or
   waymass  volume depending on what was measured and where the measuring

took place. A wey of cheese ranged from 200 to 324 pounds.

   sack     No precise definition
   spindle  The length depends on the type of yarn
   block    Defined variously on different computer systems
   erlang   A unit of telephone traffic defined variously.

Omitted because there are no other units for this dimension. Is this true? What about CCS = 1/36 erlang? Erlang is supposed to be dimensionless. One erlang means a single channel occupied for one hour.