# Physical and Chemical Symbols

The following is the meaning of the physics symbols and chemical symbols, along with their symbols and explanations:

#### In physics

Constant

α (lowercase alpha) denotes the fine structure constant (electromagnetic).
αG represents the fine structure constant of gravity.
ε0 denotes the vacuum permittivity or electric constant.
μ0 indicates vacuum magnetic permeability or magnetic constant.
σ (lowercase sigma) denotes the Stefan-Boltzmann constant.

#### In astronomy

The lowercase set of the Greek alphabet is used to denote the star in the Bayer naming system. For example, Alpha Centauri (α Cen), Gamma Cephei (γ Cep), Epsilon Eridani (ε Eri).

α (lowercase alpha) is also used to record the right-hand rise of a star, (δ is the declination, see below), which is the first equatorial coordinate.
γ (lower case gamma) is also used to denote a spring point (gamma point or “ point”); this point serves as a reference in the definition of coordinates, in the equatorial coordinate system.
δ (lowercase delta) is also used to note the declination of a star, see above).
Λ (uppercase lambda) denotes the cosmological constant, one of the parameters used to describe the evolution of the universe.
Ξ (uppercase ksi) indicates the compactness of a star, i.e. the ratio between its Schwarzschild radius (the radius that an object with the same mass would have if it were a black hole) and its actual size.
ϖ (a variant of the lower case pi) denotes the longitude of the periapsis, one of the orbital elements: ϖ = ω + Ω.
ω (lowercase omega) denotes the argument of periapsis, one of the orbital elements.
Ω (uppercase omega) designates the longitude of the ascending vertex, one of the orbital elements.

#### In chemistry

(lowercase gamma) indicates the activity coefficient in thermochemistry;
(capital delta) above the arrow in the reaction equation means the reaction was carried out by heating;
(lower case delta) denotes a chemical shift in nuclear magnetic resonance
(capital eta) shows the Eta function of Ludwig Boltzmann’s theorem H (theorem “Eta”), within the framework of the kinetic theory of gases;
(lowercase theta) indicates the temperature in degrees Celsius. Example: éb(cyclohexane) = 81°C. This symbol is mainly used to distinguish between relative temperature (in degrees Celsius) and absolute temperature (in kelvins, denoted by T): (°C) = T (K) – 273.15;
(capital kappa) denotes the Kappa index, which estimates the amount of chemical product required, during the bleaching of wood pulp, to obtain paper pulp that has a certain degree of whiteness;
(lowercase mu) indicates chemical potential in thermochemistry.
(lowercase nu) denotes the stoichiometric coefficient
(lowercase ksi) indicates the progress of a chemical reaction.
, , and are different types of covalent chemical bonds.

#### Electrochemistry

(lowercase lambda) represents the molar ionic conductivity of an ionic species such as K+.
(lowercase sigma) is used to denote the conductivity of some related ionic species such as K++Cl−. (This symbol is found for example in the formula S/l: Conductance G is equal to the conductivity multiplied by the surface of the electrolytic plate and divided by the distance between the plates; or in the formula = = Σ (λi Ci): conductivity equals the sum of the molar conductivity (see above) species multiplied by the molar concentration C).

#### In electromagnetism

(lowercase delta) indicates the length of the air gap of the magnetic material.
(lower case epsilon) denotes permittivity (specifically 0 denotes vacuum permittivity).
(lower case mu) indicates magnetic permeability (specifically 0 indicates vacuum magnetic permeability).
(lowercase sigma) indicates electrical conductivity.
(capital letter phi) denotes magnetic flux as well as electric flux.
(capital psi) is also used for electric flux, especially when it is necessary not to confuse the symbol with magnetic flux.

#### In electricity and electronics

(lowercase alpha) is used to record the temperature coefficient of an electronic or electrical component (resistor, capacitor, quartz, etc.)
(lowercase delta) is used to indicate the angle of loss (or delta tangent) of the dielectric or capacitor;
(lowercase rho) is used to express:
resistivity,
electric charge volume density;
(lowercase sigma) is used to indicate electrical conductivity;
(lower case phi) is used to record the phase shift (or phase at the origin) of an alternating current or sinusoidal signal;
(omega capital) is used to express the SI unit of electrical resistance, the ohm (Unicode \$2126).

#### In mechanics

(lowercase alpha) indicates angular acceleration;
(lower case epsilon) is used for relative elongation: = l/l ;
(lowercase eta) is often used in fluid mechanics to denote dynamic viscosity;
(lowercase symbol) is used for wavelengths;
(lowercase mu) is used:
in mechanics if fluid to show dynamic viscosity (as );
in dynamics to show the coefficient of friction (dynamic);
in statics 0 is also used to denote the coefficient of static friction;
(lowercase nu) is often used in fluid mechanics to denote kinematic viscosity;
(lowercase rho) or (lowercase mu) indicates density;
(lowercase sigma) is used
to determine angular momentum;
to determine normal tensile or compressive stresses;
(lowercase chi) is used to denote the coefficient of compressibility (thermodynamics and waves);
(omega capital) refers to the dynamics of the angular velocity of precession;
(lowercase omega) indicates the angular velocity.

#### In quantum mechanics

(capital psi) denotes the wave function (|Ψ(r)|² hence the probability density of presence).
(capital theta) indicates the angular part when described in spherical coordinates.

#### In optics and waves

(lowercase alpha) indicates angles: incident, reflection, refraction;
(lowercase letter) indicates the wavelength;
(lowercase nu) indicates the frequency, both waves and the natural frequency of an object (eg a string);
(lowercase ksi) denotes the wave function: = A sin(kx-ωt);
(lowercase sigma), indicates the wave number;
(lowercase omega) indicates the pulse (frequency multiplied by 2π).

#### Nuclear physics symbols

(lowercase alpha) is used to denote alpha particles, i.e. helium 4 nuclei;
(lowercase beta) is used in the index form + and , to denote positrons and electrons, respectively;
(lowercase gamma) is used to denote gamma radiation, and by extension photons in general;
(lower case epsilon) is often used to indicate electronic capture;
(lowercase sigma), indicates cross section

#### In thermodynamics

(lowercase alpha) indicates the coefficient of linear expansion;
(lowercase beta) denotes the coefficient equivalent to the thermodynamic temperature T (in kelvins) according to the formula , where is the Boltzmann constant;
(lowercase gamma) indicates the coefficient of volume expansion;
(lowercase theta) indicates the Celsius temperature (against T for absolute temperature);
(lowercase) indicates thermal conductivity.
(lowercase phi) is used to record the heat flux density;
(capital letter phi) indicates heat flux.

More common symbols

(small eta) is used to indicate the efficiency of energy transformation.
(lowercase nu) is used to indicate frequency.
(lowercase tau) indicates the time constant of a system.
(lowercase omega) is used to indicate the pulse: = 2 with frequency.
(capital delta) is used for the increment symbol ∆ (Unicode \$2206), which is why it is read as delta and is used to designate geometric lines, or intervals, or even variations. Example: t (delta t) indicates the duration, P (delta P) the pressure variation.

### Symbols for physical quantities and their international units

Space & Time
symbolquantitysymbolSI unit
ssdisplacement, distancemmeter
xyzcartesian coordinatesmmeter
cartesian unit vectorsunitless
r̂, θ̂, φ̂spherical unit vectorsunitless
ρ̂, φ̂, ẑcylindrical unit vectorsunitless
normal unit vectorunitless
tangential unit vectorunitless
hheight, depthmmeter
ℓ, Llengthmmeter
ddistance, separation, thicknessmmeter
tthicknessmmeter
Ddiametermmeter
Ccircumferencemmeter
AAarea, cross-sectional area, projected area, surface aream2square meter
Vvolumem3cubic meter
ttime, durationssecond
Tperiod, periodic timessecond
τtime constantssecond
ffrequencyHzhertz

#### Physics Symbols in Mechanics

Mechanics
symbolquantitysymbolSI unit
vvvelocity, speedm/smeter per second
aaaccelerationm/s2meter per second squared
acaccentripetal acceleration, centrifugal accelerationm/s2meter per second squared
gggravitational field, acceleration due to gravitym/s2meter per second squared
mmasskgkilogram
FFforceNnewton
FgWWforce of gravity, weightNnewton
FnNNnormal force, normalNnewton
Fffsfkforce of friction (static, kinetic)Nnewton
μs, μkcoefficient of friction (static, kinetic)unitless
ppmomentumkg m/skilogram meter per second
JJimpulseN snewton second
WworkJjoule
Eenergy, total energyJjoule
KKtKrkinetic energy (translational, rotational)Jjoule
UUgUspotential energy (gravitational, spring)Jjoule
Vggravitational potentialJ/kgjoule per kilogram
ηefficiencyunitless
PpowerWwatt
τ, τtorqueN mnewton meter
Imoment of inertiakg m2kilogram meter squared
LLangular momentumkg m2/skilogram meter squared per second
HHangular impulseN m snewton meter second
kspring constantN/mnewton per meter
PpressurePapascal
σnormal stressPapascal
τshear stressPapascal
ρdensity, volume mass densitykg/m3kilogram per cubic meter
σarea mass density, superficial mass densitykg/m2kilogram per square meter
λlinear mass densitykg/mkilogram per meter
FBBBbuoyancy, buoyant forceNnewton
qmmass flow ratekg/skilogram per second
qVvolume flow ratem3/scubic meter per second
FDRRdrag, aerodynamic drag, air resistanceNnewton
CCDdrag coefficient, coefficient of dragunitless
ηviscosity, dynamic viscosityPa spascal second
νkinematic viscositym2/ssquare meter per second
Mamach numberunitless
Rereynolds numberunitless
Frfroude numberunitless
Eyoung’s modulus, modulus of elasticityPapascal
Gshear modulus, modulus of rigidityPapascal
Kbulk modulus, modulus of compressionPapascal
εlinear strainunitless
γshear strainunitless
θvolume strainunitless
γsurface tensionN/mnewton per meter

#### Thermal Physics

Thermal Physics
symbolquantitysymbolSI unit
TtemperatureKkelvin
αlinear expansivity, coefficient of linear thermal expansionK−1inverse kelvin
βvolume expansivity, coefficient of volume thermal expansionK−1inverse kelvin
QheatJjoule
cspecific heat, specific heat capacityJ/kg Kjoule per kilogram kelvin
Llatent heat, specific latent heatJ/kgjoule per kilogram
namount of substancemole
Nnumber of particlesunitless
Pheat flow rateWwatt
kthermal conductivityW/m Kwatt per meter kelvin
εemissivityunitless
Uinternal energyJjoule
SentropyJ/Kjoule per kelvin
wways, number of identical microstatesunitless
COPcoefficient of performanceunitless

#### Waves and Optics

Waves & Optics
symbolquantitysymbolSI unit
λwavelengthmmeter
vcwave speedm/smeter per second
IintensityW/m2watt per square meter
LleveldB, dNpdecibel, decineper
nindex of refraction, absolute index of refractionunitless
ffocal lengthmmeter
Mmagnificationunitless

#### Electricity and Magnetism

Electricity & Magnetism
symbolquantitysymbolSI unit
qQcharge, electric chargeCcoulomb
ρcharge density, volume charge densityC/m3coulomb per cubic meter
σarea charge density, superficial charge densityC/m2coulomb per square meter
λlinear charge densityC/mcoulomb per meter
FE, FEelectric force, electrostatic forceNnewton
EEelectric fieldN/C, V/mnewton per coulomb, volt per meter
ΦEelectric fluxN m2/C, V mnewton meter squared per coulomb, volt meter
UUEpotential energy, electric potential energyJjoule
V, VEvoltage, potential, electric potentialVvolt
electromotive force, emfVvolt
κdielectric constantunitless
Icurrent, electric currentAampère
Rrresistance, electrical resistance, internal resistanceΩohm
ρresistivityΩ mohm meter
GconductanceSsiemens
σconductivityS/msiemens per meter
FB, FBmagnetic forceNnewton
BBmagnetic fieldTtesla
ΦBmagnetic fluxWbweber
Nnumber of turnsunitless
nturns per unit length, turns densitym−1inverse meter
ηenergy densityJ/m3joule per cubic meter
SSpoynting vector, intensityW/m2watt per square meter

#### Modern Physics

Modern Physics
symbolquantitysymbolSI unit
γlorentz factor, lorentz gammaunitless
φwork functionJjoule
ψ(r,t), ψ(r)φ(t)wave functionunitless
T½half lifessecond
Ddose, absorbed doseGygray
Heffective doseSvsievert

Sources: PinterPandai, Vedantu, Edrawsoft