path: root/pint/default_en.txt

# Default Pint units definition file
# Based on the International System of Units
# Language: english
# :copyright: 2013,2019 by Pint Authors, see AUTHORS for more details.

# Syntax
# ======
# Units
# -----
# <canonical name> = <relation to another unit or dimension> [= <symbol>] [= <alias>] [ = <alias> ] [...]
#
# The canonical name and aliases should be expressed in singular form.
# Pint automatically deals with plurals built by adding 's' to the singular form; plural
# forms that don't follow this rule should be instead explicitly listed as aliases.
#
# If a unit has no symbol and one wants to define aliases, then the symbol should be
# conventionally set to _.
#
# Example:
#     millennium = 1e3 * year = _ = millennia
#
#
# Prefixes
# --------
# <prefix>- = <amount> [= <symbol>] [= <alias>] [ = <alias> ] [...]
#
# Example:
#     deca- =  1e+1  = da- = deka-
#
#
# Derived dimensions
# ------------------
# [dimension name] = <relation to other dimensions>
#
# Example:
#     [density] = [mass] / [volume]
#
# Note that primary dimensions don't need to be declared; they can be
# defined for the first time in a unit definition.
# E.g. see below `meter = [length]`
#
#
# Additional aliases
# ------------------
# @alias <canonical name or previous alias> = <alias> [ = <alias> ] [...]
#
# Used to add aliases to already existing unit definitions.
# Particularly useful when one wants to enrich definitions
# from defaults_en.txt with custom aliases.
#
# Example:
#     @alias meter = my_meter

# See also: https://pint.readthedocs.io/en/latest/defining.html

@defaults
    group = international
    system = mks
@end


#### PREFIXES ####

# decimal prefixes
quecto- = 1e-30 = q-
ronto- = 1e-27 = r-
yocto- = 1e-24 = y-
zepto- = 1e-21 = z-
atto- =  1e-18 = a-
femto- = 1e-15 = f-
pico- =  1e-12 = p-
nano- =  1e-9  = n-
# The micro (U+00B5) and Greek mu (U+03BC) are both valid prefixes,
# and they often use the same glyph.
micro- = 1e-6  = µ- = μ- = u-
milli- = 1e-3  = m-
centi- = 1e-2  = c-
deci- =  1e-1  = d-
deca- =  1e+1  = da- = deka-
hecto- = 1e2   = h-
kilo- =  1e3   = k-
mega- =  1e6   = M-
giga- =  1e9   = G-
tera- =  1e12  = T-
peta- =  1e15  = P-
exa- =   1e18  = E-
zetta- = 1e21  = Z-
yotta- = 1e24  = Y-
ronna- = 1e27 = R-
quetta- = 1e30 = Q-

# binary_prefixes
kibi- = 2**10 = Ki-
mebi- = 2**20 = Mi-
gibi- = 2**30 = Gi-
tebi- = 2**40 = Ti-
pebi- = 2**50 = Pi-
exbi- = 2**60 = Ei-
zebi- = 2**70 = Zi-
yobi- = 2**80 = Yi-

# extra_prefixes
semi- = 0.5 = _ = demi-
sesqui- = 1.5


#### BASE UNITS ####

meter = [length] = m = metre
second = [time] = s = sec
ampere = [current] = A = amp
candela = [luminosity] = cd = candle
gram = [mass] = g
mole = [substance] = mol
kelvin = [temperature]; offset: 0 = K = degK = °K = degree_Kelvin = degreeK  # older names supported for compatibility
radian = [] = rad
bit = []
count = []


#### CONSTANTS ####

@import constants_en.txt


#### UNITS ####
# Common and less common, grouped by quantity.
# Conversion factors are exact (except when noted),
# although floating-point conversion may introduce inaccuracies

# Angle
turn = 2 * π * radian = _ = revolution = cycle = circle
degree = π / 180 * radian = deg = arcdeg = arcdegree = angular_degree
arcminute = degree / 60 = arcmin = arc_minute = angular_minute
arcsecond = arcminute / 60 = arcsec = arc_second = angular_second
milliarcsecond = 1e-3 * arcsecond = mas
grade = π / 200 * radian = grad = gon
mil = π / 32000 * radian

# Solid angle
steradian = radian ** 2 = sr
square_degree = (π / 180) ** 2 * sr = sq_deg = sqdeg

# Information
baud = bit / second = Bd = bps

byte = 8 * bit = B = octet
# byte = 8 * bit = _ = octet
## NOTE: B (byte) symbol can conflict with Bell

# Ratios
percent = 0.01 = %
ppm = 1e-6

# Length
angstrom = 1e-10 * meter = Å = ångström = Å
micron = micrometer = µ = μ
fermi = femtometer = fm
light_year = speed_of_light * julian_year = ly = lightyear
astronomical_unit = 149597870700 * meter = au  # since Aug 2012
parsec = 1 / tansec * astronomical_unit = pc
nautical_mile = 1852 * meter = nmi
bohr = hbar / (alpha * m_e * c) = a_0 = a0 = bohr_radius = atomic_unit_of_length = a_u_length
x_unit_Cu = K_alpha_Cu_d_220 * d_220 / 1537.4 = Xu_Cu
x_unit_Mo = K_alpha_Mo_d_220 * d_220 / 707.831 = Xu_Mo
angstrom_star = K_alpha_W_d_220 * d_220 / 0.2090100 = Å_star
planck_length = (hbar * gravitational_constant / c ** 3) ** 0.5

# Mass
metric_ton = 1e3 * kilogram = t = tonne
unified_atomic_mass_unit = atomic_mass_constant = u = amu
dalton = atomic_mass_constant = Da
grain = 64.79891 * milligram = gr
gamma_mass = microgram
carat = 200 * milligram = ct = karat
planck_mass = (hbar * c / gravitational_constant) ** 0.5

# Time
minute = 60 * second = min
hour = 60 * minute = h = hr
day = 24 * hour = d
week = 7 * day
fortnight = 2 * week
year = 365.25 * day = a = yr = julian_year
month = year / 12

# decade = 10 * year
## NOTE: decade [time] can conflict with decade [dimensionless]

century = 100 * year = _ = centuries
millennium = 1e3 * year = _ = millennia
eon = 1e9 * year
shake = 1e-8 * second
svedberg = 1e-13 * second
atomic_unit_of_time = hbar / E_h = a_u_time
gregorian_year = 365.2425 * day
sidereal_year = 365.256363004 * day                # approximate, as of J2000 epoch
tropical_year = 365.242190402 * day                # approximate, as of J2000 epoch
common_year = 365 * day
leap_year = 366 * day
sidereal_day = day / 1.00273790935079524           # approximate
sidereal_month = 27.32166155 * day                 # approximate
tropical_month = 27.321582 * day                   # approximate
synodic_month = 29.530589 * day = _ = lunar_month  # approximate
planck_time = (hbar * gravitational_constant / c ** 5) ** 0.5

# Temperature
degree_Celsius = kelvin; offset: 273.15 = °C = celsius = degC = degreeC
degree_Rankine = 5 / 9 * kelvin; offset: 0 = °R = rankine = degR = degreeR
degree_Fahrenheit = 5 / 9 * kelvin; offset: 233.15 + 200 / 9 = °F = fahrenheit = degF = degreeF
degree_Reaumur = 4 / 5 * kelvin; offset: 273.15 = °Re = reaumur = degRe = degreeRe = degree_Réaumur = réaumur
atomic_unit_of_temperature = E_h / k = a_u_temp
planck_temperature = (hbar * c ** 5 / gravitational_constant / k ** 2) ** 0.5

# Area
[area] = [length] ** 2
are = 100 * meter ** 2
barn = 1e-28 * meter ** 2 = b
darcy = centipoise * centimeter ** 2 / (second * atmosphere)
hectare = 100 * are = ha

# Volume
[volume] = [length] ** 3
liter = decimeter ** 3 = l = L = litre
cubic_centimeter = centimeter ** 3 = cc
lambda = microliter = λ
stere = meter ** 3

# Frequency
[frequency] = 1 / [time]
hertz = 1 / second = Hz
revolutions_per_minute = revolution / minute = rpm
revolutions_per_second = revolution / second = rps
counts_per_second = count / second = cps

# Wavenumber
[wavenumber] = 1 / [length]
reciprocal_centimeter = 1 / cm = cm_1 = kayser

# Velocity
[velocity] = [length] / [time]
[speed] = [velocity]
knot = nautical_mile / hour = kt = knot_international = international_knot
mile_per_hour = mile / hour = mph = MPH
kilometer_per_hour = kilometer / hour = kph = KPH
kilometer_per_second = kilometer / second = kps
meter_per_second = meter / second = mps
foot_per_second = foot / second = fps

# Volumetric Flow Rate
[volumetric_flow_rate] = [volume] / [time]
sverdrup = 1e6 * meter ** 3 / second = sv

# Acceleration
[acceleration] = [velocity] / [time]
galileo = centimeter / second ** 2 = Gal

# Force
[force] = [mass] * [acceleration]
newton = kilogram * meter / second ** 2 = N
dyne = gram * centimeter / second ** 2 = dyn
force_kilogram = g_0 * kilogram = kgf = kilogram_force = pond
force_gram = g_0 * gram = gf = gram_force
force_metric_ton = g_0 * metric_ton = tf = metric_ton_force = force_t = t_force
atomic_unit_of_force = E_h / a_0 = a_u_force

# Energy
[energy] = [force] * [length]
joule = newton * meter = J
erg = dyne * centimeter
watt_hour = watt * hour = Wh = watthour
electron_volt = e * volt = eV
rydberg = ℎ * c * R_inf = Ry
hartree = 2 * rydberg = E_h = Eh = hartree_energy = atomic_unit_of_energy = a_u_energy
calorie = 4.184 * joule = cal = thermochemical_calorie = cal_th
international_calorie = 4.1868 * joule = cal_it = international_steam_table_calorie
fifteen_degree_calorie = 4.1855 * joule = cal_15
british_thermal_unit = 1055.056 * joule = Btu = BTU = Btu_iso
international_british_thermal_unit = 1e3 * pound / kilogram * degR / kelvin * international_calorie = Btu_it
thermochemical_british_thermal_unit = 1e3 * pound / kilogram * degR / kelvin * calorie = Btu_th
quadrillion_Btu = 1e15 * Btu = quad
therm = 1e5 * Btu = thm = EC_therm
US_therm = 1.054804e8 * joule  # approximate, no exact definition
ton_TNT = 1e9 * calorie = tTNT
tonne_of_oil_equivalent = 1e10 * international_calorie = toe
atmosphere_liter = atmosphere * liter = atm_l

# Power
[power] = [energy] / [time]
watt = joule / second = W
volt_ampere = volt * ampere = VA
horsepower = 550 * foot * force_pound / second = hp = UK_horsepower = hydraulic_horsepower
boiler_horsepower = 33475 * Btu / hour                            # unclear which Btu
metric_horsepower = 75 * force_kilogram * meter / second
electrical_horsepower = 746 * watt
refrigeration_ton = 12e3 * Btu / hour = _ = ton_of_refrigeration  # approximate, no exact definition
cooling_tower_ton = 1.25 * refrigeration_ton # approximate, no exact definition
standard_liter_per_minute = atmosphere * liter / minute = slpm = slm
conventional_watt_90 = K_J90 ** 2 * R_K90 / (K_J ** 2 * R_K) * watt = W_90

# Momentum
[momentum] = [length] * [mass] / [time]

# Density (as auxiliary for pressure)
[density] = [mass] / [volume]
mercury = 13.5951 * kilogram / liter = Hg = Hg_0C = Hg_32F = conventional_mercury
water = 1.0 * kilogram / liter = H2O = conventional_water
mercury_60F = 13.5568 * kilogram / liter = Hg_60F   # approximate
water_39F = 0.999972 * kilogram / liter = water_4C  # approximate
water_60F = 0.999001 * kilogram / liter             # approximate

# Pressure
[pressure] = [force] / [area]
pascal = newton / meter ** 2 = Pa
barye = dyne / centimeter ** 2 = Ba = barie = barad = barrie = baryd
bar = 1e5 * pascal
technical_atmosphere = kilogram * g_0 / centimeter ** 2 = at
torr = atm / 760
pound_force_per_square_inch = force_pound / inch ** 2 = psi
kip_per_square_inch = kip / inch ** 2 = ksi
millimeter_Hg = millimeter * Hg * g_0 = mmHg = mm_Hg = millimeter_Hg_0C
centimeter_Hg = centimeter * Hg * g_0 = cmHg = cm_Hg = centimeter_Hg_0C
inch_Hg = inch * Hg * g_0 = inHg = in_Hg = inch_Hg_32F
inch_Hg_60F = inch * Hg_60F * g_0
inch_H2O_39F = inch * water_39F * g_0
inch_H2O_60F = inch * water_60F * g_0
foot_H2O = foot * water * g_0 = ftH2O = feet_H2O
centimeter_H2O = centimeter * water * g_0 = cmH2O = cm_H2O
sound_pressure_level = 20e-6 * pascal = SPL

# Torque
[torque] = [force] * [length]
foot_pound = foot * force_pound = ft_lb = footpound

# Viscosity
[viscosity] = [pressure] * [time]
poise = 0.1 * Pa * second = P
reyn = psi * second

# Kinematic viscosity
[kinematic_viscosity] = [area] / [time]
stokes = centimeter ** 2 / second = St

# Fluidity
[fluidity] = 1 / [viscosity]
rhe = 1 / poise

# Amount of substance
particle = 1 / N_A = _ = molec = molecule

# Concentration
[concentration] = [substance] / [volume]
molar = mole / liter = M

# Catalytic activity
[activity] = [substance] / [time]
katal = mole / second = kat
enzyme_unit = micromole / minute = U = enzymeunit

# Entropy
[entropy] = [energy] / [temperature]
clausius = calorie / kelvin = Cl

# Molar entropy
[molar_entropy] = [entropy] / [substance]
entropy_unit = calorie / kelvin / mole = eu

# Radiation
becquerel = counts_per_second = Bq
curie = 3.7e10 * becquerel = Ci
rutherford = 1e6 * becquerel = Rd
gray = joule / kilogram = Gy
sievert = joule / kilogram = Sv
rads = 0.01 * gray
rem = 0.01 * sievert
roentgen = 2.58e-4 * coulomb / kilogram = _ = röntgen  # approximate, depends on medium

# Heat transimission
[heat_transmission] = [energy] / [area]
peak_sun_hour = 1e3 * watt_hour / meter ** 2 = PSH
langley = thermochemical_calorie / centimeter ** 2 = Ly

# Luminance
[luminance] = [luminosity] / [area]
nit = candela / meter ** 2
stilb = candela / centimeter ** 2
lambert = 1 / π * candela / centimeter ** 2

# Luminous flux
[luminous_flux] = [luminosity]
lumen = candela * steradian = lm

# Illuminance
[illuminance] = [luminous_flux] / [area]
lux = lumen / meter ** 2 = lx

# Intensity
[intensity] = [power] / [area]
atomic_unit_of_intensity = 0.5 * ε_0 * c * atomic_unit_of_electric_field ** 2 = a_u_intensity

# Current
biot = 10 * ampere = Bi
abampere = biot = abA
atomic_unit_of_current = e / atomic_unit_of_time = a_u_current
mean_international_ampere = mean_international_volt / mean_international_ohm = A_it
US_international_ampere = US_international_volt / US_international_ohm = A_US
conventional_ampere_90 = K_J90 * R_K90 / (K_J * R_K) * ampere = A_90
planck_current = (c ** 6 / gravitational_constant / k_C) ** 0.5

# Charge
[charge] = [current] * [time]
coulomb = ampere * second = C
abcoulomb = 10 * C = abC
faraday = e * N_A * mole
conventional_coulomb_90 = K_J90 * R_K90 / (K_J * R_K) * coulomb = C_90
ampere_hour = ampere * hour = Ah

# Electric potential
[electric_potential] = [energy] / [charge]
volt = joule / coulomb = V
abvolt = 1e-8 * volt = abV
mean_international_volt = 1.00034 * volt = V_it  # approximate
US_international_volt = 1.00033 * volt = V_US    # approximate
conventional_volt_90 = K_J90 / K_J * volt = V_90

# Electric field
[electric_field] = [electric_potential] / [length]
atomic_unit_of_electric_field = e * k_C / a_0 ** 2 = a_u_electric_field

# Electric displacement field
[electric_displacement_field] = [charge] / [area]

# Reduced electric field
[reduced_electric_field] = [electric_field] * [area]
townsend =  1e-21 * V * m^2 = Td

# Resistance
[resistance] = [electric_potential] / [current]
ohm = volt / ampere = Ω
abohm = 1e-9 * ohm = abΩ
mean_international_ohm = 1.00049 * ohm = Ω_it = ohm_it  # approximate
US_international_ohm = 1.000495 * ohm = Ω_US = ohm_US   # approximate
conventional_ohm_90 = R_K / R_K90 * ohm = Ω_90 = ohm_90

# Resistivity
[resistivity] = [resistance] * [length]

# Conductance
[conductance] = [current] / [electric_potential]
siemens = ampere / volt = S = mho
absiemens = 1e9 * siemens = abS = abmho

# Capacitance
[capacitance] = [charge] / [electric_potential]
farad = coulomb / volt = F
abfarad = 1e9 * farad = abF
conventional_farad_90 = R_K90 / R_K * farad = F_90

# Magnetic flux
[magnetic_flux] = [electric_potential] * [time]
weber = volt * second = Wb
unit_pole = µ_0 * biot * centimeter

# Inductance
[inductance] = [magnetic_flux] / [current]
henry = weber / ampere = H
abhenry = 1e-9 * henry = abH
conventional_henry_90 = R_K / R_K90 * henry = H_90

# Magnetic field
[magnetic_field] = [magnetic_flux] / [area]
tesla = weber / meter ** 2 = T
gamma = 1e-9 * tesla = γ

# Magnetomotive force
[magnetomotive_force] = [current]
ampere_turn = ampere = At
biot_turn = biot
gilbert = 1 / (4 * π) * biot_turn = Gb

# Magnetic field strength
[magnetic_field_strength] = [current] / [length]

# Electric dipole moment
[electric_dipole] = [charge] * [length]
debye = 1e-9 / ζ * coulomb * angstrom = D  # formally 1 D = 1e-10 Fr*Å, but we generally want to use it outside the Gaussian context

# Electric quadrupole moment
[electric_quadrupole] = [charge] * [area]
buckingham = debye * angstrom

# Magnetic dipole moment
[magnetic_dipole] = [current] * [area]
bohr_magneton = e * hbar / (2 * m_e) = µ_B = mu_B
nuclear_magneton = e * hbar / (2 * m_p) = µ_N = mu_N

# Logaritmic Unit Definition
#  Unit = scale; logbase; logfactor
#  x_dB = [logfactor] * log( x_lin / [scale] ) / log( [logbase] )

# Logaritmic Units of dimensionless quantity: [ https://en.wikipedia.org/wiki/Level_(logarithmic_quantity) ]

decibelmilliwatt = 1e-3 watt; logbase: 10; logfactor: 10 = dBm
decibelmicrowatt = 1e-6 watt; logbase: 10; logfactor: 10 = dBu

decibel = 1 ; logbase: 10; logfactor: 10 = dB
# bell = 1 ; logbase: 10; logfactor: = B
## NOTE: B (Bell) symbol conflicts with byte

decade = 1 ; logbase: 10; logfactor: 1
## NOTE: decade [time] can conflict with decade [dimensionless]

octave = 1 ; logbase: 2; logfactor: 1 = oct

neper = 1 ; logbase: 2.71828182845904523536028747135266249775724709369995; logfactor: 0.5 = Np
# neper = 1 ; logbase: eulers_number; logfactor: 0.5 = Np

#### UNIT GROUPS ####
# Mostly for length, area, volume, mass, force
# (customary or specialized units)

@group USCSLengthInternational
    thou = 1e-3 * inch = th = mil_length
    inch = yard / 36 = in = international_inch = inches = international_inches
    hand = 4 * inch
    foot = yard / 3 = ft = international_foot = feet = international_feet
    yard = 0.9144 * meter = yd = international_yard  # since Jul 1959
    mile = 1760 * yard = mi = international_mile

    circular_mil = π / 4 * mil_length ** 2 = cmil
    square_inch = inch ** 2 = sq_in = square_inches
    square_foot = foot ** 2 = sq_ft = square_feet
    square_yard = yard ** 2 = sq_yd
    square_mile = mile ** 2 = sq_mi

    cubic_inch = in ** 3 = cu_in
    cubic_foot = ft ** 3 = cu_ft = cubic_feet
    cubic_yard = yd ** 3 = cu_yd
@end

@group USCSLengthSurvey
    link = 1e-2 * chain = li = survey_link
    survey_foot = 1200 / 3937 * meter = sft
    fathom = 6 * survey_foot
    rod = 16.5 * survey_foot = rd = pole = perch
    chain = 4 * rod
    furlong = 40 * rod = fur
    cables_length = 120 * fathom
    survey_mile = 5280 * survey_foot = smi = us_statute_mile
    league = 3 * survey_mile

    square_rod = rod ** 2 = sq_rod = sq_pole = sq_perch
    acre = 10 * chain ** 2
    square_survey_mile = survey_mile ** 2 = _ = section
    square_league = league ** 2

    acre_foot = acre * survey_foot = _ = acre_feet
@end

@group USCSDryVolume
    dry_pint = bushel / 64 = dpi = US_dry_pint
    dry_quart = bushel / 32 = dqt = US_dry_quart
    dry_gallon = bushel / 8 = dgal = US_dry_gallon
    peck = bushel / 4 = pk
    bushel = 2150.42 cubic_inch = bu
    dry_barrel = 7056 cubic_inch = _ = US_dry_barrel
    board_foot = ft * ft * in = FBM = board_feet = BF = BDFT = super_foot = superficial_foot = super_feet = superficial_feet
@end

@group USCSLiquidVolume
    minim = pint / 7680
    fluid_dram = pint / 128 = fldr = fluidram = US_fluid_dram = US_liquid_dram
    fluid_ounce = pint / 16 = floz = US_fluid_ounce = US_liquid_ounce
    gill = pint / 4 = gi = liquid_gill = US_liquid_gill
    pint = quart / 2 = pt = liquid_pint = US_pint
    fifth = gallon / 5 = _ = US_liquid_fifth
    quart = gallon / 4 = qt = liquid_quart = US_liquid_quart
    gallon = 231 * cubic_inch = gal = liquid_gallon = US_liquid_gallon
@end

@group USCSVolumeOther
    teaspoon = fluid_ounce / 6 = tsp
    tablespoon = fluid_ounce / 2 = tbsp
    shot = 3 * tablespoon = jig = US_shot
    cup = pint / 2 = cp = liquid_cup = US_liquid_cup
    barrel = 31.5 * gallon = bbl
    oil_barrel = 42 * gallon = oil_bbl
    beer_barrel = 31 * gallon = beer_bbl
    hogshead = 63 * gallon
@end

@group Avoirdupois
    dram = pound / 256 = dr = avoirdupois_dram = avdp_dram = drachm
    ounce = pound / 16 = oz = avoirdupois_ounce = avdp_ounce
    pound = 7e3 * grain = lb = avoirdupois_pound = avdp_pound
    stone = 14 * pound
    quarter = 28 * stone
    bag = 94 * pound
    hundredweight = 100 * pound = cwt = short_hundredweight
    long_hundredweight = 112 * pound
    ton = 2e3 * pound = _ = short_ton
    long_ton = 2240 * pound
    slug = g_0 * pound * second ** 2 / foot
    slinch = g_0 * pound * second ** 2 / inch = blob = slugette

    force_ounce = g_0 * ounce = ozf = ounce_force
    force_pound = g_0 * pound = lbf = pound_force
    force_ton = g_0 * ton = _ = ton_force = force_short_ton = short_ton_force
    force_long_ton = g_0 * long_ton = _ = long_ton_force
    kip = 1e3 * force_pound
    poundal = pound * foot / second ** 2 = pdl
@end

@group AvoirdupoisUK using Avoirdupois
    UK_hundredweight = long_hundredweight = UK_cwt
    UK_ton = long_ton
    UK_force_ton = force_long_ton = _ = UK_ton_force
@end

@group AvoirdupoisUS using Avoirdupois
    US_hundredweight = hundredweight = US_cwt
    US_ton = ton
    US_force_ton = force_ton = _ = US_ton_force
@end

@group Troy
    pennyweight = 24 * grain = dwt
    troy_ounce = 480 * grain = toz = ozt
    troy_pound = 12 * troy_ounce = tlb = lbt
@end

@group Apothecary
    scruple = 20 * grain
    apothecary_dram = 3 * scruple = ap_dr
    apothecary_ounce = 8 * apothecary_dram = ap_oz
    apothecary_pound = 12 * apothecary_ounce = ap_lb
@end

@group ImperialVolume
    imperial_minim = imperial_fluid_ounce / 480
    imperial_fluid_scruple = imperial_fluid_ounce / 24
    imperial_fluid_drachm = imperial_fluid_ounce / 8 = imperial_fldr = imperial_fluid_dram
    imperial_fluid_ounce = imperial_pint / 20 = imperial_floz = UK_fluid_ounce
    imperial_gill = imperial_pint / 4 = imperial_gi = UK_gill
    imperial_cup = imperial_pint / 2 = imperial_cp = UK_cup
    imperial_pint = imperial_gallon / 8 = imperial_pt = UK_pint
    imperial_quart = imperial_gallon / 4 = imperial_qt = UK_quart
    imperial_gallon = 4.54609 * liter = imperial_gal = UK_gallon
    imperial_peck = 2 * imperial_gallon = imperial_pk = UK_pk
    imperial_bushel = 8 * imperial_gallon = imperial_bu = UK_bushel
    imperial_barrel = 36 * imperial_gallon = imperial_bbl = UK_bbl
@end

@group Printer
    pica = inch / 6 = _ = printers_pica
    point = pica / 12 = pp = printers_point = big_point = bp
    didot = 1 / 2660 * m
    cicero = 12 * didot
    tex_point = inch / 72.27
    tex_pica = 12 * tex_point
    tex_didot = 1238 / 1157 * tex_point
    tex_cicero = 12 * tex_didot
    scaled_point = tex_point / 65536
    css_pixel = inch / 96 = px

    pixel = [printing_unit] = _ = dot = pel = picture_element
    pixels_per_centimeter = pixel / cm = PPCM
    pixels_per_inch = pixel / inch = dots_per_inch = PPI = ppi = DPI = printers_dpi
    bits_per_pixel = bit / pixel = bpp
@end

@group Textile
    tex = gram / kilometer = Tt
    dtex = decitex
    denier = gram / (9 * kilometer) = den
    jute = pound / (14400 * yard) = Tj
    aberdeen = jute = Ta
    RKM  = gf / tex

    number_english = 840 * yard / pound = Ne = NeC = ECC
    number_meter = kilometer / kilogram = Nm
@end


#### CGS ELECTROMAGNETIC UNITS ####

# === Gaussian system of units ===
@group Gaussian
    franklin = erg ** 0.5 * centimeter ** 0.5 = Fr = statcoulomb = statC = esu
    statvolt = erg / franklin = statV
    statampere = franklin / second = statA
    gauss = dyne / franklin = G
    maxwell = gauss * centimeter ** 2 = Mx
    oersted = dyne / maxwell = Oe = ørsted
    statohm = statvolt / statampere = statΩ
    statfarad = franklin / statvolt = statF
    statmho = statampere / statvolt
@end
# Note this system is not commensurate with SI, as ε_0 and µ_0 disappear;
# some quantities with different dimensions in SI have the same
# dimensions in the Gaussian system (e.g. [Mx] = [Fr], but [Wb] != [C]),
# and therefore the conversion factors depend on the context (not in pint sense)
[gaussian_charge] = [length] ** 1.5 * [mass] ** 0.5 / [time]
[gaussian_current] = [gaussian_charge] / [time]
[gaussian_electric_potential] = [gaussian_charge] / [length]
[gaussian_electric_field] = [gaussian_electric_potential] / [length]
[gaussian_electric_displacement_field] = [gaussian_charge] / [area]
[gaussian_electric_flux] = [gaussian_charge]
[gaussian_electric_dipole] = [gaussian_charge] * [length]
[gaussian_electric_quadrupole] = [gaussian_charge] * [area]
[gaussian_magnetic_field] = [force] / [gaussian_charge]
[gaussian_magnetic_field_strength] = [gaussian_magnetic_field]
[gaussian_magnetic_flux] = [gaussian_magnetic_field] * [area]
[gaussian_magnetic_dipole] = [energy] / [gaussian_magnetic_field]
[gaussian_resistance] = [gaussian_electric_potential] / [gaussian_current]
[gaussian_resistivity] = [gaussian_resistance] * [length]
[gaussian_capacitance] = [gaussian_charge] / [gaussian_electric_potential]
[gaussian_inductance] = [gaussian_electric_potential] * [time] / [gaussian_current]
[gaussian_conductance] = [gaussian_current] / [gaussian_electric_potential]
@context Gaussian = Gau
    [gaussian_charge] -> [charge]: value / k_C ** 0.5
    [charge] -> [gaussian_charge]: value * k_C ** 0.5
    [gaussian_current] -> [current]: value / k_C ** 0.5
    [current] -> [gaussian_current]: value * k_C ** 0.5
    [gaussian_electric_potential] -> [electric_potential]: value * k_C ** 0.5
    [electric_potential] -> [gaussian_electric_potential]: value / k_C ** 0.5
    [gaussian_electric_field] -> [electric_field]: value * k_C ** 0.5
    [electric_field] -> [gaussian_electric_field]: value / k_C ** 0.5
    [gaussian_electric_displacement_field] -> [electric_displacement_field]: value / (4 * π / ε_0) ** 0.5
    [electric_displacement_field] -> [gaussian_electric_displacement_field]: value * (4 * π / ε_0) ** 0.5
    [gaussian_electric_dipole] -> [electric_dipole]: value / k_C ** 0.5
    [electric_dipole] -> [gaussian_electric_dipole]: value * k_C ** 0.5
    [gaussian_electric_quadrupole] -> [electric_quadrupole]: value / k_C ** 0.5
    [electric_quadrupole] -> [gaussian_electric_quadrupole]: value * k_C ** 0.5
    [gaussian_magnetic_field] -> [magnetic_field]: value / (4 * π / µ_0) ** 0.5
    [magnetic_field] -> [gaussian_magnetic_field]: value * (4 * π / µ_0) ** 0.5
    [gaussian_magnetic_flux] -> [magnetic_flux]: value / (4 * π / µ_0) ** 0.5
    [magnetic_flux] -> [gaussian_magnetic_flux]: value * (4 * π / µ_0) ** 0.5
    [gaussian_magnetic_field_strength] -> [magnetic_field_strength]: value / (4 * π * µ_0) ** 0.5
    [magnetic_field_strength] -> [gaussian_magnetic_field_strength]: value * (4 * π * µ_0) ** 0.5
    [gaussian_magnetic_dipole] -> [magnetic_dipole]: value * (4 * π / µ_0) ** 0.5
    [magnetic_dipole] -> [gaussian_magnetic_dipole]: value / (4 * π / µ_0) ** 0.5
    [gaussian_resistance] -> [resistance]: value * k_C
    [resistance] -> [gaussian_resistance]: value / k_C
    [gaussian_resistivity] -> [resistivity]: value * k_C
    [resistivity] -> [gaussian_resistivity]: value / k_C
    [gaussian_capacitance] -> [capacitance]: value / k_C
    [capacitance] -> [gaussian_capacitance]: value * k_C
    [gaussian_inductance] -> [inductance]: value * k_C
    [inductance] -> [gaussian_inductance]: value / k_C
    [gaussian_conductance] -> [conductance]: value / k_C
    [conductance] -> [gaussian_conductance]: value * k_C
@end

# === ESU system of units ===
#   (where different from Gaussian)
#   See note for Gaussian system too
@group ESU using Gaussian
    statweber = statvolt * second = statWb
    stattesla = statweber / centimeter ** 2 = statT
    stathenry = statweber / statampere = statH
@end
[esu_charge] = [length] ** 1.5 * [mass] ** 0.5 / [time]
[esu_current] = [esu_charge] / [time]
[esu_electric_potential] = [esu_charge] / [length]
[esu_magnetic_flux] = [esu_electric_potential] * [time]
[esu_magnetic_field] = [esu_magnetic_flux] / [area]
[esu_magnetic_field_strength] = [esu_current] / [length]
[esu_magnetic_dipole] = [esu_current] * [area]
@context ESU = esu
    [esu_magnetic_field] -> [magnetic_field]: value * k_C ** 0.5
    [magnetic_field] -> [esu_magnetic_field]: value / k_C ** 0.5
    [esu_magnetic_flux] -> [magnetic_flux]: value * k_C ** 0.5
    [magnetic_flux] -> [esu_magnetic_flux]: value / k_C ** 0.5
    [esu_magnetic_field_strength] -> [magnetic_field_strength]: value / (4 * π / ε_0) ** 0.5
    [magnetic_field_strength] -> [esu_magnetic_field_strength]: value * (4 * π / ε_0) ** 0.5
    [esu_magnetic_dipole] -> [magnetic_dipole]: value / k_C ** 0.5
    [magnetic_dipole] -> [esu_magnetic_dipole]: value * k_C ** 0.5
@end


#### CONVERSION CONTEXTS ####

@context(n=1) spectroscopy = sp
    # n index of refraction of the medium.
    [length] <-> [frequency]: speed_of_light / n / value
    [frequency] -> [energy]: planck_constant * value
    [energy] -> [frequency]: value / planck_constant
    # allow wavenumber / kayser
    [wavenumber] <-> [length]: 1 / value
@end

@context boltzmann
    [temperature] -> [energy]: boltzmann_constant * value
    [energy] -> [temperature]: value / boltzmann_constant
@end

@context energy
    [energy] -> [energy] / [substance]: value * N_A
    [energy] / [substance] -> [energy]: value / N_A
    [energy] -> [mass]: value / c ** 2
    [mass] -> [energy]: value * c ** 2
@end

@context(mw=0,volume=0,solvent_mass=0) chemistry = chem
    # mw is the molecular weight of the species
    # volume is the volume of the solution
    # solvent_mass is the mass of solvent in the solution

    # moles -> mass require the molecular weight
    [substance] -> [mass]: value * mw
    [mass] -> [substance]: value / mw

    # moles/volume -> mass/volume and moles/mass -> mass/mass
    # require the  molecular weight
    [substance] / [volume] -> [mass] / [volume]: value * mw
    [mass] / [volume] -> [substance] / [volume]: value / mw
    [substance] / [mass] -> [mass] / [mass]: value * mw
    [mass] / [mass] -> [substance] / [mass]: value / mw

    # moles/volume -> moles requires the solution volume
    [substance] / [volume] -> [substance]: value * volume
    [substance] -> [substance] / [volume]: value / volume

    # moles/mass -> moles requires the solvent (usually water) mass
    [substance] / [mass] -> [substance]: value * solvent_mass
    [substance] -> [substance] / [mass]: value / solvent_mass

    # moles/mass -> moles/volume require the solvent mass and the volume
    [substance] / [mass] -> [substance]/[volume]: value * solvent_mass / volume
    [substance] / [volume] -> [substance] / [mass]: value / solvent_mass * volume

@end

@context textile
    # Allow switching between Direct count system (i.e. tex) and
    # Indirect count system (i.e. Ne, Nm)
    [mass] / [length] <-> [length] / [mass]: 1 / value
@end


#### SYSTEMS OF UNITS ####

@system SI
    second
    meter
    kilogram
    ampere
    kelvin
    mole
    candela
@end

@system mks using international
    meter
    kilogram
    second
@end

@system cgs using international, Gaussian, ESU
    centimeter
    gram
    second
@end

@system atomic using international
    # based on unit m_e, e, hbar, k_C, k
    bohr: meter
    electron_mass: gram
    atomic_unit_of_time: second
    atomic_unit_of_current: ampere
    atomic_unit_of_temperature: kelvin
@end

@system Planck using international
    # based on unit c, gravitational_constant, hbar, k_C, k
    planck_length: meter
    planck_mass: gram
    planck_time: second
    planck_current: ampere
    planck_temperature: kelvin
@end

@system imperial using ImperialVolume, USCSLengthInternational, AvoirdupoisUK
    yard
    pound
@end

@system US using USCSLiquidVolume, USCSDryVolume, USCSVolumeOther, USCSLengthInternational, USCSLengthSurvey, AvoirdupoisUS
    yard
    pound
@end