| Quantity |
Dimension |
Alternatives |
Root definition and Notes |
| Basic SI quantities |
| Length |
m |
m |
meter |
| Mass |
kg |
kg |
kilogram |
| Time |
s |
s |
second |
| Current, electric |
A |
A |
ampere |
| Temperature |
K |
K |
kelvin |
| Quantity of substance |
mol |
mol |
mole |
| Luminosity | Luminous intensity |
cd |
cd |
candle |
| Pseudo-dimensional quantities: |
| Plane angle |
1 |
rad |
radian |
| Solid angle |
1 |
sr |
steradian |
| Universal dimensionless quantities |
| Count of events | Number of instances |
1 |
|
This covers all kinds of enumerations |
| Probability of an event |
1 |
|
Real number in a dimensionless interval [0,1] |
| Ratio of commensurable quantities |
1 |
|
Q1/Q2, with Q1 and Q2 having the same dimension |
| Relative variation |
1 |
|
ΔQ/Q, for any quantity Q |
| Logarithmic ratio logb(A/A') in any base b |
1 |
|
Applicable to any ratio of commensurable quantities |
| Logarithmic scale differential | Relative differential |
1 |
|
d{ln(Q)} = dQ/Q, for any quantity Q |
| Pseudo-dimensional quantities: |
| Phase | Phase angle |
1 |
rad |
φ typically in exp(i(ωt+φ)) |
| Logarithmic ratio Log(P/P')/10 |
1 |
dB |
decibel. Uses base-10 logarithm. Applies to power P |
| Logarithmic ratio Log(X/X')/20 |
1 |
dB |
decibel. Uses base-10 logarithm. Applies to amplitudes X |
| Gain or Loss of a device |
1 |
usually in dB |
[Output]/[Input], provided they are commensurable quantities |
| Attenuation | Amplification (generic) |
1 |
usually in dB |
[Quantity(p)]/[Quantity(p')], with p being some parameter |
| Logarithmic ratio ln(A/A') |
1 |
Np |
Neper. Uses natural logarithm |
| Logarithmic scale probability density |
1 |
1/Np |
[Probability]/[Natural-logarithmic ratio] |
| Operators |
| Derivative with respect to time |
s-1 |
|
d/dt, ∂/∂t |
| Derivative with respect to a length |
m-1 |
|
d/dr, ∂/∂r, r = x | y | z |
| Nabla ( ∇ ) | div | grad | rot | curl |
m-1 |
|
Any derivative-like construct with respect to a distance |
| Laplace operator | Laplacian |
m-2 |
|
∇2 = ∂2/∂x2 + ∂2/∂y2 + ∂2/∂z2 |
| D'Alembert operator | D'Alembertian |
m-2 |
|
(1/c2)∂2/∂t2 - ∂2/∂x2 - ∂2/∂y2 - ∂2/∂z2 |
| Multiple derivatives with respect to time |
s-p |
|
dp/dtp, ∂p/∂tp; for p = 1,2,3,.. |
| Multiple derivatives with respect to a length |
m-p |
|
dp/drp, ∂p/∂rp; for p = 1,2,3,..., r = x | y | z |
| Quantities related only to time |
| Time | Duration |
s |
s |
second |
| Half life |
s |
|
of a non-conservative / decaying quantity |
| Settling time |
s |
typically dB/s |
Used to describe transient phenomena |
| Relaxation time |
s |
|
Used for returns to equilibria |
| Activity | Frequency of events |
s-1 |
|
[Counts]/[Time] |
| Count rate | Expectation frequency |
s-1 |
|
[Counts]/[Time] |
| Relative growth rate |
s-1 |
|
[Relative variation]/[Time] |
| Relative evolution rate | Log-scale evolution rate |
s-1 |
|
d{ln(Q)}/dt = (dQ/dt)/Q |
| Settling rate |
s-1 |
typically dB/s |
[Ratio]/[ΔTime]. Used for transient phenomena |
| Relaxation rate |
s-1 |
|
1/[Relaxation time] |
| Frequency of waves |
s-1 |
Hz |
hertz |
| Phase drift rate |
s-1 |
rad.s-1 |
[Phase angle]/[Time] |
| Angular velocity / speed |
s-1 |
rad.s-1 |
[Plane angle]/[Time] |
| Frequency drift rate |
s-2 |
Hz.s-1 |
[ΔFrequency]/[Time]. Applicable to waves |
| Angular acceleration / deceleration |
s-2 |
rad.s-2 |
[ΔAngularVelocity]/[Time] |
| Quantities related only to space |
| Position vector |
m |
|
in all Euclidean n-dimensional spaces |
| Length | Distance |
m |
m |
meter |
| Perimeter | Circumference | Radius |
m |
|
|
| Thickness |
m |
|
usually referred to planar structures |
| Wavelength |
m |
|
[Wave velocity]/[Frequency] |
| Wavenumber |
m-1 |
|
[Number of waves]/[Distance] |
| K-space vector | Reciprocal space position |
m-1 |
|
|
| Curvature radius |
m |
|
of a line in plane/space or surface in space |
| Curvature |
m-1 |
|
1/[Curvature radius] |
| Convergence |
m-1 |
dioptry |
used in optics, but not only .. |
| Attenuation / amplification over a distance |
m-1 |
dB/m |
[Attenuation]/[Distance]. Mostly in acoustic and electronics |
| Extinction coefficient |
m-1 |
dB/m |
[Ratio]/m. Used mostly for radiation |
| Propagation / transmission loss |
m-1 |
dB/m |
[Ratio]/m. Generic, usable for any quantity |
| Area | Cross section |
m2 |
|
[Distance]*[Distance] |
| Surface element | Surface area |
m2 |
|
[Distance]*[Distance]. Applicable to 3D bodies |
| Volume element | Volume |
m3 |
|
[Area]*[Distance] |
| Propagation through space and time |
| Velocity | Speed |
m.s-1 |
|
[Distance]/[Time] |
| Acceleration | Deceleration |
m.s-2 |
|
[ΔVelocity]/[ΔTime] |
| Drift speed |
m.s-1 |
|
Steady-state speed of an object |
| Surface / area growth rate |
m2.s-1 |
|
[ΔArea]/[Time] |
| Volume growth rate |
m3.s-1 |
|
[ΔVolume]/[Time]. For example, of a crystal |
| Volume flow |
m3.s-1 |
|
[Volume]/[Time]. For example, through a device |
| Matter distribution and transport |
| Particle density |
m-3 |
|
[Count]/[Volume]. Obsolete: number density |
| Mass |
kg |
kg |
kilogram |
| Mass production rate |
kg.s-1 |
|
[ΔMass]/[Time] |
| Mass density | Specific density |
kg.m-3 |
|
[Mass]/[Volume] |
| Mass density gradient | Specific density gradient |
kg.m-4 |
|
[Mass density]/[Distance] |
| Specific volume |
m3.kg-1 |
|
[Volume]/[Mass] |
| Concentration ratio by volume |
1 |
Dimensionless |
[Partial volume]/[Total volume] |
| Concentration ratio by mass |
1 |
Dimensionless |
[Partial mass]/[Total mass]. Not by weight: obsolete) |
| Mass flow (total) |
kg.s-1 |
|
[ΔMass]/[Time]. For example, through a device |
| Diffusion coefficient |
m2.s-1 |
|
[Distance2]/[Time] |
| Molar distribution and transport quantities: |
| Particle count, molar |
mol-1 |
|
[Count]/[Mol]. For example, the Avogadro constant |
| Molar production rate |
mol.s-1 |
|
[ΔQuantity]/[Time] |
| Molar mass |
kg.mol-1 |
|
[Mass]/[Quantity] |
| Molar volume |
m3.mol-1 |
|
[Volume]/[Quantity] |
| Molar density | Density of substance |
m-3.mol |
|
[Quantity]/[Volume] |
| Molarity | Concentration |
m-3.mol |
|
[Quantity]/[Volume]. Same as molar density |
| Molarity gradient | Concentration gradient |
m-4.mol |
|
[Molarity]/[Distance] |
| Molar concentration ratio |
1 |
Dimensionless |
[Partial quantity]/[Total quantity] |
| Molality (intended as concentration) |
kg-1.mol |
mol/kg |
[Quantity]/[Mass]. Obsolete |
| Katalytic activity |
mol.s-1 |
katal |
[ΔQuantity]/[Time] |
| Mechanics and hydrodynamics |
| Force |
kg.m.s-2 |
N |
newton. [Mass]*[Acceleration] |
| Moment of motion |
kg.m.s-1 |
|
[Mass]*[Velocity], [Mass flow]*[Distance] |
| Impulse |
kg.m.s-1 |
|
[ΔMoment of motion], [Force]*[ΔTime], [Mass]*[ΔVelocity] |
| Moment of force | Torque |
kg.m2.s-2 |
N.m |
[Force]*[Distance]. Like energy |
| Couple |
kg.m2.s-2 |
N.m |
2*[Force]*[Distance] for two non-aligned opposing forces |
| Pressure |
kg.m-1.s-2 |
N.m-2, Pa |
pascal. [Force]/[Area] |
| Pressure gradient |
kg.m-2.s-2 |
N.m-3, Pa/m |
[Pressure]/[Distance] |
| Energy | Lagrangian | Hamiltonian |
kg.m2.s-2 |
N.m, J |
joule. [Force]*[Distance], [Power]*[Time] |
| Specific energy |
m2.s-2 |
J.kg-1 |
[Energy]/[Mass] |
| Energy density |
kg.m-1.s-2 |
J.m-3 |
[Energy]/[Volume] |
| Power | Energy flux |
kg.m2.s-3 |
J.s-1, W |
watt. [ΔEnergy]/[ΔTime] |
| Action |
kg.m2.s-1 |
J.s |
[Energy]*[Time], [Moment of motion]*[Distance] |
| Angular moment of inertia |
kg.m2 |
|
[Mass]*[Distance2] |
| Angular moment of motion |
kg.m2.s-1 |
J.s |
[Moment of motion]*[Distance] |
| Circulation |
m2.s-1 |
J.s.kg-1 |
[Angular moment]/[Mass], [Velocity]*[Loop length] |
| Spin |
1 |
Dimensionless |
of a quantum particle |
| Stress | Tension | Compression |
kg.m-1.s-2 |
N.m-2, Pa (pascal) |
[Force]/[Area]. ... same as pressure |
| Compressive strength |
kg.m-1.s-2 |
N.m-2, Pa |
[Force]/[Area]. Like pressure |
| Strain (mechanical) |
1 |
Dimensionless |
[ΔLength]/[Length] Relative deformation |
| Friction |
kg.m.s-2 |
N |
Tangential force between two moving surfaces |
| Traction |
kg.m.s-2 |
N |
Maximum tangential force before slipping |
| Velocity, superficial |
m.s-1 |
m/s |
In porous media; as if the space was filled only by the fluid |
| Velocity, advection |
m.s-1 |
m/s |
In porous media; actual progress along pressure gradient |
| Wave function for N particles (quantum) |
m-3N/2 |
tentative |
|ψ|2dτN is a dimensionless probability element. |
| Mechanical and hydrodynamic properties of matter |
| Compressibility | Modulus of compression |
kg-1.m.s2 |
Pa-1 |
[Pressure]/([ΔVolume]/[Volume]). Inverse of bulk modulus |
| Bulk modulus |
kg.m-1.s-2 |
N.m-2, Pa |
([ΔVolume]/[Volume])/[Pressure]. Inverse of compressibility |
| Young modulus |
kg.m-1.s-2 |
N.m-2, Pa |
[Stress]/[Strain]. Like shear modulus |
| Shear modulus | Modulus of rigidity |
kg.m-1.s-2 |
N.m-2, Pa |
[Stress]/[Strain]. Same dimension aas Young modulus |
| Poisson's ratio |
1 |
Dimensionless |
[Transversal striction]/[Londitudinal elongation] |
| Impact | Notch resistance |
kg.s-2 |
J.m-2 |
[Energy]/[Area] |
| Hardness | Tensile strength |
kg.m-1.s-2 |
N.m-2, Pa |
[Force]/[Area]. Like pressure |
| Stiffness (linear) |
kg.s-2 |
N.m-1 |
[Force]/[Displacement]. ... of a structure |
| Stiffness (rotational) |
kg.m2.s-2.rad-1 |
N.m.rad-1 |
[Moment of force]/[Angle]. ... of a structure |
| Friction coefficient |
1 |
Dimensionless |
[Tangential force]/[Normal force] |
| Traction coefficient |
1 |
Dimensionless |
[Traction]/[Weight] |
| Self-diffusion coefficient |
m2.s-1 |
|
[Distance2]/[Time] |
| Surface tension |
kg.s-2 |
N/m |
[Force]/[Length]. Same as surface energy |
| Surface energy |
kg.s-2 |
J/m2 |
[Energy]/[Area]. Same as surface tension |
| Viscosity, dynamic |
kg.m-1.s-1 |
Pa.s |
([Force]/[Area])/[ΔVelocity] |
| Viscosity, kinematic |
m2.s-1 |
|
[Dynamic viscosity]/[Density] |
| Reynolds number |
1 |
Dimensionless |
[Velocity]*[length]/[Kinematic viscosity] |
| Critical angle of repose |
rad |
or degree |
Steepest angle of a slope before a slide |
| Porosity, volume |
1 |
Dimensionless |
[Volume of pores]/[Total volume], in porous media |
| Porosity, superficial |
1 |
Dimensionless |
[Void cross section]/[Total cross section], in porous media |
| Permeability, hydraulic |
m2 |
1 darcy = 10-12 m2 |
[Velocity]*[Viscosity]/[Pressure gradient], in porous media |
| Conductivity, hydraulic |
m.s-1 |
m/s |
Used for porous media |
| Specific acoustic impedance / resistance / reactance |
kg.m-2.s-1 |
Pa.s/m , reyl |
[ΔPressure]*[Velocity], intensive property |
| Specific acoustic conductance / susceptance |
kg-1.m2.s |
reyl-1 |
Inverse of specific acoustic impedance |
| Acoustic impedance / resistance / reactance |
kg.m-4.s-1 |
Pa.s/m3, reyl/m2 |
[ΔPressure]/[Volume flow rate], extensive property |
| Thermodynamics |
| Temperature |
K |
K |
kelvin |
| Temperature gradient | Thermal gradient |
K.m-1 |
|
[ΔTemperature]/[Distance] |
| Heat | Internal energy | Enthalpy |
kg.m2.s-2 |
J |
Same as energy |
| Specific heat | internal energy | enthalpy |
m2.s-2 |
J.kg-1 |
[Heat]/[Mass] |
| Heat capacity |
kg.m2.s-2.K-1 |
J.K-1 |
[ΔHeat]/[ΔTemperature] |
| Heat flux |
kg.m2.s-3 |
J.s, W |
[ΔHeat]/[ΔTime]. Same as power |
| Heat flux density | Irradiance |
kg.s-3 |
W.m-2 |
[Heat flux]/[Area] |
| Entropy |
kg.m2.s-2.K-1 |
J.K-1 |
[ΔHeat]/[Temperature] |
| Specific entropy |
m2.s-2.K-1 |
J.K-1.kg-1 |
[Entropy]/[Mass] |
| Free energy | Free enthalpy |
kg.m2.s-2 |
J |
Helmholtz | Gibbs functions, respectively |
| Specific free energy | free enthalpy |
m2.s-2 |
J.kg-1 |
[Energy]/[Mass]. Also specific Helmholtz | Gibbs functions |
| Molar thermodynamical quantities: |
| Molar heat | internal energy | enthalpy |
kg.m2.s-2.mol-1 |
J.mol-1 |
[Heat]/[Quantity] |
| Molar energy |
kg.m2.s-2.mol-1 |
J.mol-1 |
[Energy]/[Quantity] |
| Molar entropy |
kg.m2.s-2.K-1.mol-1 |
J.K-1.mol-1 |
[Entropy]/[Quantity] |
| Molar free energy | free enthalpy |
kg.m2.s-2.mol-1 |
J.mol-1 |
[Energy]/[Quantity]. Molar versions of the above |
| Thermodynamic and thermal properties of matter |
| Thermal expansion coefficient |
K-1 |
|
([ΔLength]/[Length])/[Temperature] |
| Heat capacity, specific |
m2.s-2.K-1 |
J.K-1.kg-1 |
[Heat capacity]/[Mass] |
| Heat capacity, molar |
kg.m2.s-2.K-1.mol-1 |
J.K-1.mol-1 |
[Heat capacity]/[Quantity] |
| Heat of fusion | evaporation, specific |
m2.s-2 |
J.kg-1 |
[Energy]/[Mass] |
| Heat of fusion | evaporation, molar |
kg.m2.s-2.mol-1 |
J.mol-1 |
[Energy]/[Quantity] |
| Heat conductivity |
kg.m.s-3.K-1 |
W.m-1.K-1 |
[Heat flux]/([Distance]*[ΔTemperature]) |
| Thermal diffusivity |
m2.s-1 |
|
([∂Temp]/[∂Time])/[∇2Temp]. |
| Prandtl number |
1 |
Dimensionless |
[Kinematic viscosity]/[Thermal diffusivity] |
| Joule-Thomson coefficient |
kg-1.m.s2.K |
K.Pa-1 |
[ΔTemperature]/[ΔPressure] |
| Pi coefficient, molar |
kg.m-1.s-2.mol-1 |
J.m-3 |
[ΔInternalEnergy]/[ΔVolume] |
| Chemical potential, molar |
kg.m2.s-2.mol-1 |
J.mol-1 |
[ΔInternalEnergy]/[ΔQuantity] |
| Softening point |
K |
|
Temperature at which hardness drops below a level |
| Annealing point |
K |
|
Temperature at which viscosity drops below 1012 Pa.s |
| Strain point |
K |
|
Temperature at which viscosity drops below 1013.5 Pa.s |
| Flash point |
K |
|
Temperature at which vapour can be kept burning |
| Fire point |
K |
|
Temperature at which ignited vapour keeps burning |
| Thermal properties of devices |
| Thermal resistance |
kg-1.m-2.s3K |
K/W |
[ΔT]/[Power]. |
| Electromagnetism |
| Charge, electric |
s.A |
C |
coulomb. [Current]*[Time] |
| Charge density |
m-3.s.A |
C.m-3 |
[Charge]/[Volume] |
| Current, electric |
A |
A |
ampere. [Charge]/[Time] |
| Current density | Current intensity |
m-2.A |
|
[Current]/[Area] |
| Specific charge | Charge/mass ratio |
kg-1.s.A |
C.kg-1 |
[Charge]/[Mass] |
| Molar charge |
s.A.mol-1 |
C.mol-1 |
[Charge]/[Quantity] |
| Quantum charge |
1 |
Dimensionless |
[Charge]/[Elementary charge quantum] |
| Surface density of charge |
m-2.s.A |
C.m-2 |
[Charge]/[Area] |
| Potential, electric |
kg.m2.s-3.A-1 |
W.A-1, J.C-1, C.F-1, V |
volt. [Power]/[Current], [Energy]/[Charge] |
| Electric dipole moment |
m.s.A |
C.m |
[Charge]*[Distance] |
| Electric quadrupole moment |
m2.s.A |
C.m2 |
[Electric dipole]*[Distance], [Electric charge]*[Distance2] |
| Electric field strength | Electric intensity |
kg.m.s-3.A-1 |
V.m-1 |
[ΔPotential]/[Distance] |
| Electric field gradient |
kg.s-3.A-1 |
V.m-2 |
[ΔEl.field strength]/[Distance] |
| Electric flux density | Electric induction |
m-2.s.A |
C.m-2 |
[Charge]/[Area] |
| Electric polarization | Electric displacement |
m-2.s.A |
C.m-2 |
[Charge]/[Area]. Same as electric flux density |
| Magnetic field strength | Magnetic intensity |
m-1.A |
|
[Current]/[Distance] |
| Magnetic flux |
kg.m2.s-2.A-1 |
V.s, W.s.A-1, Wb |
weber. [ΔPotential]*[Time], [Power]/[dCurrent/dt] |
| Magnetic flux density | Magnetic induction |
kg.s-2.A-1 |
Wb.m-2, T |
tesla. [Mag.flux]/[Area] |
| Magnetic vector potential |
kg.m.s-2.A-1 |
m-1.s.V, m.T |
[Mag.flux density]*[Distance], [El.field strength]*[Time] |
| Magnetization |
m-1.A |
|
[Magnetic moment]/[Volume]. Like magnetic field strength |
| Magnetic charge (bound) |
m-2.A |
|
- ∇.[Magnetization] , -Divergence of magnetization |
| Poynting vector |
kg.s-3 |
W.m-2 |
[El.field strength]/[Mag.field strength]. Same as irradiance |
| Magnetic field gradient |
kg.m-1.s-2.A-1 |
T.m-1 |
[ΔMagnetic flux density]/[Distance] |
| Magnetic dipole moment |
m2.A |
J.T-1 |
[Current]*[Area]. Same as magnetic moment |
| Magnetic quadrupole moment |
m3.A |
m.J.T-1 |
[Magnetic dipole]*[Distance] |
| Gyromagnetic ratio |
kg-1.s.A |
Hz.T-1 |
[Mag.moment]/[Angular moment of motion] |
| Magnetogyric ratio |
kg.s-1.A-1 |
T.Hz-1 |
[Angular moment of motion]/[Mag.moment] |
| Relativistic four-current (Jα) |
m-2.A |
|
Like current density and [Charge]*[c] |
| Relativistic four-potential (Aα) |
kg.m.s-2.A-1 |
m-1.s.V, m.T |
Like magnetic vector potential and [El.potential]/[c] |
| Relativistic electromagnetic field tensor (Fμν) |
kg.s-2.A-1 |
T |
Like magnetic flux density |
| Relativistic displacement four-tensor (Dμν) |
m-1.A |
|
Like magnetic intensity |
| Electromagnetic properties of matter |
| Resistivity |
kg.m3.s-3.A-2 |
Ω.m |
[Resistance]*[Length])/[Area] |
| Conductivity |
kg-1.m-3.s3.A2 |
S.m-1 |
1/[Resistivity] |
| Permittivity, electric |
kg-1.m-3.s4.A2 |
F.m-1 |
[El.flux density]/[El.field strength] |
| Dielectric constant | Relative permittivity |
1 |
Dimensionless |
[Permittivity]/[Permittivity of vacuum] |
| Permeability, magnetic |
kg.m.s-2.A-2 |
N.A-2, H.m-1 |
[Mag.flux density]/[Mag.field strength] |
| Reluctance, magnetic |
kg-1.m-1.s2.A2 |
m.H-1 |
1/[Permeability] |
| Relative permeability, magnetic |
1 |
Dimensionless |
[Permeability]/[Permeability of vacuum] |
| Susceptibility, magnetic |
1 |
Dimensionless |
[Relative permeability] - 1 |
| Characteristic impedance |
kg.m2.s-3.A-2 |
V.A-1, Ω, ohm |
√([Mag.Permeability]/[El.Permittivity]) |
| Electric | Dielectric strength | rigidity |
kg.m.s-3.A-1 |
V.m-1 |
[ΔPotential]/[Distance] |
| Verdet constant |
kg-1.m-1.s2.A1 |
rad.m-1.T-1 |
([Angle]/[Length])/[Magnetic flux density] |
| Work function |
kg.m2.s-2 |
J, eV |
[Energy] needed to remove an electron |
| Thermoelectric power | Thermopower |
kg.m2.s-3.A-1.K-1 |
V.K-1 |
[ΔPotential]/[ΔTemperature] |
| Seeback coefficient |
kg.m2.s-3.A-1.K-1 |
V.K-1 |
[ΔPotential]/[ΔTemperature] |
| Thomson coefficient |
kg.m2.s-3.A-1.K-1 |
W.K-1.A-1 |
[Heat flux]/([ΔTemperature]*[Current]) |
| Peltier coefficient |
kg.m2.s-3.A-1 |
W.A-1, V |
[Heat flux]/[Current] |
| Piezzoelectric coefficient |
kg.m.s-3.A-1 |
V.m-1 |
[El.field strength]/([ΔLength]/[Length]) |
| Electrostriction coefficient |
kg-2.m-2.s6.A2 |
m2.V-2 |
([ΔVolume]/[Volume])/[El.field strength]2 |
| g-factor of a particle |
1 |
Dimensionless |
[Mag.moment]/([Spin].[Bohr magneton]) |
| Properties of electric/magnetic devices and circuit components |
| Bandwidth |
s-1 |
Hz |
[ΔFrequency] |
| Voltage | Electromotive force (emf) |
kg.m2.s-3.A-1 |
V |
[ΔPotential] |
| Current, electric |
A |
A |
ampere. [Charge]/[Time] |
| Magnetomotive force (mmf) |
A |
|
[Current]*[Number of turns] |
| Impedance, of a circuit |
kg.m2.s-3.A-2 |
Ω |
ohm |
| Admittance, of a circuit |
kg-1.m-2.s3.A2 |
S |
siemens. 1/[Circuit impedance] |
| Resistance |
kg.m2.s-3.A-2 |
V.A-1, Ω(ohm) |
[ΔPotential]/[Current] |
| Conductance |
kg-1.m-2.s3.A2 |
A.V-1, S (siemens) |
1/[Resistance] |
| Capacitance |
kg-1.m-2.s4.A2 |
C.V-1, F |
farad. [Charge]/[ΔPotential] |
| Reactance, capacitive |
kg.m2.s-3.A-2 |
Ω (ohm) |
1/(i[Angular frequency].[Capacitance]) |
| Susceptance, capacitive |
kg-1.m-2.s3.A2 |
S (siemens) |
1/[Reactance] |
| Inductance | Mutual inductance |
kg.m2.s-2.A-2 |
V.s.A-1, Wb.A-1, H |
henry. [ΔPotential]/[dCurrent/dt] or [Magnetic flux]/[Current] |
| Impedance, inductive |
kg.m2.s-3.A-2 |
Ω (ohm) |
i[Angular frequency].[Inductance] |
| Admittance, inductive |
kg-1.m-2.s3.A2 |
S (siemens) |
1/[Inductive impedance] |
| Number of turns |
1 |
|
Applicable to coils, transformers, etc |
| Current noise, variance nJ2 |
s.A2 |
A2/Hz |
[Current]2/[Bandwidth] |
| Voltage noise, variance nV2 |
kg2.m4.s-5.A-2 |
V2/Hz |
[Voltage]2/[Bandwidth] |
| Chemistry, physical chemistry, atomic and molecular physics |
| Concentration | Molar density | Molarity |
m-3.mol |
|
[Quantity]/[Volume]. Same as Density of substance |
| Molality |
kg-1.mol |
mol/kg |
[Quantity]/[Mass] |
| Katalytic activity | Molar production rate |
mol.s-1 |
katal |
[Quantity]/[Time] |
| Molar mass |
kg.mol-1 |
|
[Mass]/[Quantity] |
| Molar charge |
s.A.mol-1 |
C.mol-1 |
[Charge]/[Quantity] |
| Molecular | ionic quantum charge |
1 |
Dimensionless |
[Charge of a molecule or ion]/[Elementary charge quantum] |
| Ionic strength | Ionic force |
m-3.mol |
|
Sum([Conc.]*[Ionic quantum charge]2) |
| Ion mobility |
kg-1.m-1.s2.A |
m2.s-1.V-1 |
[Velocity]/[Electric field strength] . |
| Drift speed |
m.s-1 |
|
Steady-state speed of ions in electric field . |
| Fugacity |
kg.m-1.s-2 |
Pa |
Effective pressure in real gases |
| Osmotic pressure |
kg.m-1.s-2 |
Pa |
|
| Thermodynamic force |
kg.m.s-2.mol-1 |
N/mol |
[ΔChemical potential]/[Distance] |
| Chemico-physical properties of elements |
| Atomic number |
1 |
Dimensionless |
Number of protons in an atomic nucleus |
| Atomic weight | Relative atomic mass |
au |
atomic units |
Average over a typical isotopic composition |
| Mass number of an isotope |
1 |
Dimensionless |
Number of protons+neutrons in the isotope nuclide |
| Electronegativity, Pauling χ |
1 |
Dimensionless |
Relative tendency of an atom to attract electrons; χ(H)=2.20. |
| Electron affinity (always molar) |
kg.m2.s-2.mol-1 |
J.mol-1 |
Energy released when binding an electron |
| Chemico-physical properties of matter |
| Ionization energy, molar |
kg.m2.s-2.mol-1 |
J.mol-1 |
Energy to ionize a molecule/atom |
| Volume, molar |
m3.mol-1 |
|
[Volume]/[Quantity] |
| Heat of fusion | evaporation, molar |
kg.m2.s-2.mol-1 |
J.mol-1 |
[Energy]/[Quantity] |
| Chemical potential, molar |
kg.m2.s-2.mol-1 |
J.mol-1 |
[ΔInternalEnergy]/[ΔQuantity] |
| Solubility, molar |
m-3.mol |
|
[Quantity]/[Volume] |
| Reduction | Redox potential |
kg.m2.s-3.A-1 |
V (volt) |
|
| Conductivity, molar |
kg-1.s3.A2.mol-1 |
S.m2.mol-1 |
[El.conductivity]/[Concentration] |
| Relaxivity, molar |
s-1.mol-1 |
|
[Relaxation rate]/[Concentration] |
| Ebullioscopic constant |
kg.mol-1.K |
K/(mol/kg) |
[ΔTemperature]/[Molality] |
| Cryoscopic constant |
kg.mol-1.K |
K/(mol/kg) |
[ΔTemperature]/[Molality] |
| Compression factor of a real gas |
1 |
Dimensionless |
pV/(nRT). For ideal gas equals 1; temperature dependent |
| van der Waals constant: a |
kg.m5.s-2.mol-2 |
Pa.m6 |
a in (p+a/V2)(V-b)=RT, where V is molar volume |
| van der Waals constant: b |
m3.mol-1 |
|
b in (p+a/V2)(V-b)=RT, where V is molar volume |
| Virial coefficient: second |
m3.mol-1 |
|
B in pV/(nRT)=1+B(n/V)+C(n/V)2+D(n/V)3+... |
| Virial coefficient: third |
m6.mol-2 |
|
C in pV/(nRT)=1+B(n/V)+C(n/V)2+D(n/V)3+... |
| Virial coefficient: fourth |
m9.mol-3 |
|
C in pV/(nRT)=1+B(n/V)+C(n/V)2+D(n/V)3+... |
| Gravitation, Astronomy, Cosmology |
| Gravitational field intensity | Gravity |
m.s-2 |
|
[Force]/[Mass], Same as acceleration |
| Gravitational field potential |
m2.s-2 |
|
[Energy]/[Mass] |
| Gravitational constant G |
kg-1.m3.s-2 |
|
[Force]*[Distance]2/[Mass]2. Appears in Newton's equation |
| Mean motion |
s-1 |
|
Of a body on a Kepler orbit; sqrt(G(M1+M2)/r3) |
| Mean anomaly |
1 |
Dimensionless |
Of a body on a Kepler orbit; t.sqrt(G(M1+M2)/r3) |
| Star magnitude (astronomy) |
1 |
Dimensionless |
m-m'= -100.4(S/S'). S,S' are luminous fluxes of two stars |
| Cosmological constant Λ |
m-2 |
|
Appears in Einstein's equation |
| Cosmological expansion rate |
s-1 |
km/s/Mpc |
[Velocity]/[Distance]. Mpc stands for Megaparsec |
| Optics |
| Albedo, of a surface |
1 |
Dimensionless |
[Reflected elmag power]/[Incident elmag power] |
| Convergence |
m-1 |
dioptry |
dioptry |
| Luminosity | Luminous intensity |
cd |
cd |
candle or lumen/sr |
| Luminous flux | Luminous power |
cd.sr |
lm |
lumen. [Luminosity]*[Solid angle] |
| Luminance |
cd.m-2 |
|
[Luminosity]/[Area] |
| Luminous energy |
cd.sr.s |
lm.s |
[Luminous flux]*[Time]. Also known as talbot |
| Illuminance |
cd.sr.m-2 |
lm.m-2, lx |
lux. [Luminous flux]/[Area] |
| Luminous emittance |
cd.sr.m-2 |
lm.m-2, lx |
lux. Same as illuminance, but for sources |
| Luminous efficacy |
cd.sr.kg-1.m-1.s3 |
lm/W |
[Luminous flux]/[Power] |
| Luminous efficiency | Luminous coefficient |
1 |
Dimensionless |
[Luminous efficacy]/[683 lm/W] |
| Irradiance |
kg.s-3 |
W.m-2 |
[Power]/[Area]. For all kinds of energy deposition |
| Radiance |
kg.s-3.sr-1 |
W.m-2.sr-1 |
([Power]/[Area])/[Solid angle] |
| Optical properties of matter |
| Extinction coefficient |
m-1 |
|
|
| Refractive index |
1 |
Dimensionless |
Light speeds ratio (in medium)/(in vacuum) |
| Specific refractivity |
m3.kg-1 |
|
[(r2-1)/(r2+2)]/[Specific density], where r is refractive index |
| Molar refractivity |
m3.mol-1 |
|
[(r2-1)/(r2+2)]/[Concentration] |
| Dispersivity quotient |
m-1 |
|
[ΔRefractive index]/[ΔWavelength] |
| Dispersive power |
1 |
Dimensionless |
Ratio of differences of refractive indices |
| Constringence | Abbé number | V-number |
1 |
Dimensionless |
VD = (nD-1)/(nF-nC) |
| Radiation and radioactivity |
| Radioactivity | Activity |
s-1 |
Bq |
bequerel. [Counts]/[Time] |
| Irradiance |
kg.s-3 |
W.m-2 |
[Power]/[Area]. For all kinds of energy deposition |
| Absorbed dose |
m2.s-2 |
J.kg-1, Gy |
gray. [Energy]/[Mass] |
| Absorbed dose rate |
m2.s-3 |
Gy.s-1 |
[Absorbed dose]/[Time] |
| Absorbed dose equivalent |
m2.s-2 |
J.kg-1, Sv |
sievert. [const].[Energy]/[Mass] |
| Exposure |
kg-1.s.A |
C.kg-1 |
[Charge]/[Mass]. For ionising radiations |
| Radiation properties of matter |
| Half life |
s |
|
Of a radioisotope |
| Radiation power |
m2.s-3 |
W/kg |
[Power]/[Mass]. Heat generated by a radioisotope |
| Radiation power, molar |
kg.m2.s-3.mol-1 |
W/mol |
[Power]/[Quantity]. Heat generated by a radioisotope |
| Informatics |
| Information |
bit-1 |
bit |
bit; the elementary information quantum |
| Baud rate | Information flux |
bit.s-1 |
Baud |
baud. [Information]/[Time] |
| Economy and finance |
| Transactions count |
1 |
Dimensionless |
All kinds of counts |
| Interest |
1 |
% |
[ΔWealth]/[Wealth]. Usually expressed as percentage |
| Wealth | Asset |
cur |
currency |
Currencies like $, EUR, Yuan, ... are different units |
| Debt | Liability |
cur |
currency |
Usually intended as negative wealth |
| Value | Price |
cur |
currency |
Prefixes: K..thousands, M..millions, B..billions |
| Transaction value | Sale | Purchase |
cur |
currency |
Often used: mean and total values |
| Time period |
s |
year,quarter,month |
Abbrevs: mrq.. most recent quarter, ttm.. trailing twelve months |
| Fiscal year | Calendar year |
s |
year |
Abbrevs: lfy.. last fiscal year, yoy.. year over year |
| Transactions rate | Activity |
s-1 |
1/year |
[Transactions]/[Time period] |
| Transactions volume | Sales flow |
cur.s-1 |
|
[Value]/[Time period]. For example $/day or Eur/year |
| Velocity / circulation of money |
s-1 |
1/year |
[Transactions]/[Time period] |
| Interest rate |
s-1 |
%/year |
[Interest]/[Time period] |
| Return on asset / equity |
s-1 |
%/year |
([ΔValue]/[Value])/[Time period] |
| Cash flow | Flow (generic) |
cur.s-1 |
currency/year |
[Value]/[ΔTime]. Mathematically, time derivative |
| Earnings | Income rate |
cur.s-1 |
currency/year |
[Value]/[Time period] |
| GDP Gross domestic product |
cur.s-1 |
currency/year |
[Earnings]. Usually refered to nations/states/admin.regions |
| Debt/GDP ratio |
s |
year |
[Debt]/[Earnings]. Independent of currency / population size |
| P/E Price/Earnings ratio |
s |
year |
[Value]/[Earnings]. Used to assess an asset/company |
| Bond duration |
s |
year |
In general, the duration of a fixed cash flow |
