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About the Common uses in PhysicsEdit

While these are indeed common usages, it should be pointed out that there are many other usages and that other letters are used for the same purpose. The reason is quite simple: there are only so many symbols in the Greek and Latin alphabets, and scientists and mathematicians generally do not use symbols from other languages. It is a common trap to associate a symbol exclusively with some particular meaning, rather than learning and understanding the physics and relations behind it.


Greek Alphabet
Capital Lower case Name Common use in Physics
    alpha Angular acceleration
Linear expansion
Coefficient
Alpha particle (helium nucleus)
Fine Structure Constant
    beta Beta particle — high energy electron
Sound intensity
    gamma Gamma ray (high energy EM wave)
Ratio of heat capacities (in an ideal gas)
Relativistic correction factor

Shear strain

    delta Δ="Change in"
δ="Infinitesimal change in (), also used to denote the Dirac delta function (reference needed)"
    epsilon Emissivity
Strain (Direct e.g. tensile or compression)
Permittivity
EMF
    zeta (no common use)
    eta Viscosity
Energy efficiency
    theta Angle (°, rad)
Temperature
    iota The lower case   is rarely used, while   is sometimes used for the identity matrix or the moment of inertia. Note that   is not to be confused with the Roman character   (which has a dot and is much more widely used in mathematics and physics).
    kappa Spring constant
Dielectric constant
    lambda Wavelength
Thermal conductivity
Constant
Eigenvalue of a matrix
Linear density
    mu Coefficient of friction
Electrical mobility
Reduced mass
Permeability
    nu Frequency
    xi Damping cofficient
    omicron (no common use)
    pi Product symbol  
Circle number  
    rho Volume density
Resistivity
    sigma Sum symbol
Boltzmann constant
Electrical conductivity
Uncertainty
Stress (Direct e.g. tensile, compression)
Surface density
    tau Torque
Tau particle (a lepton)
Time constant

Shear stress

    upsilon mass to light ratio
    phi Magnetic/electric flux
Angle (°, rad)
    chi Rabi frequency (lasers)
Susceptibility
    psi Wave function
    omega Ohms (unit of electrical resistance)
ω Angular velocity

See AlsoEdit