List of common physics notations

This is a list of common physical constants and variables, and their notations. Note that bold text indicates that the quantity is a vector.

Latin characters

Symbol Meaning SI unit of measure
$\mathbf {A}$ magnetic vector potential
$A$ area square meters (m2)
amplitude meter
atomic mass number
$\mathbf {a}$ acceleration meters per second squared (m/s2)
$\mathbf {B}$ magnetic flux density
also called the magnetic field density or magnetic induction
tesla (T), or equivalently,
weber per square meter (Wb/m2)
$C$ capacitance farad (F)
heat capacity joule per kelvin (J⋅K−1)
constant of integration varied depending on context
$c$ speed of light (in vacuum) 299,792,458 meter per second (m/s)
speed of sound 340.29 meter per second (m/s)
specific heat capacity joule per kilogram per kelvin (J⋅kg−1⋅K−1)
viscous damping coefficient kilogram per second (kg/s)
$\mathbf {D}$ electric displacement field
also called the electric flux density
coulomb per square meter (C/m2)
$D$ density kilograms per cubic meter (kg/m3)
$d$ distance meter (m)
direction unitless
impact parameter meter (m)
diameter meter (m)
differential (e.g. $dx$ )
$d\mathbf {A}$ differential vector element of surface area A, with infinitesimally small magnitude and direction normal to surface S square meter (m2)
$dV$ differential element of volume V enclosed by surface S cubic meter (m3)
$\mathbf {E}$ electric field newton per coulomb (N⋅C−1), or equivalently, volt per meter (V⋅m−1)
$E$ energy joule (J)
Young's Modulus pascal (Pa) or newton per square meter (N/m2)
$e$ eccentricity unitless
2.71828... (base of the natural logarithm) unitless
elementary charge coulomb (C)
$\mathbf {F}$ force newton (N)
$F$ Faraday constant coulombs per mole (C⋅mol−1)
$f$ frequency hertz (Hz)
function
friction newton (N)
$G$ the gravitational constant newton meter squared per kilogram squared (N⋅m2/kg2)
$g$ acceleration due to gravity meter per second squared (m/s2), or equivalently, newton per kilogram (N/kg)
$\mathbf {H}$ magnetic field strength ampere per meter (A/m)
$H$ Hamiltonian joule (J)
$h$ height meter (m)
Planck constant joule second (J⋅s)
$\hbar$ reduced Planck constant joule second (J⋅s)
$I$ action joule second (J⋅s)
intensity watt per square meter (W/m2)
sound intensity watt per square meter (W/m2)
electric current ampere (A)
moment of inertia kilogram meter squared (kg⋅m2)
$i$ intensity watt per square meter (W/m2)
imaginary unit
$\mathbf {\hat {i}}$ Cartesian x-axis basis unit vector unitless
$\mathbf {J}$ free current density (not including bound currents due to polarization or magnetization) ampere per square meter (A/m2)
impulse kilogram meter per second (kg⋅m/s)
$j$ imaginary unit (electrical)
jerk meters per second cubed (m/s3)
$\mathbf {\hat {j}}$ Cartesian y-axis basis unit vector unitless
$K$ kinetic energy joule (J)
$k$ Boltzmann constant joule per kelvin (J/K)
wavenumber, wave vector radians per meter (m−1)
stiffness newtons per meter (N⋅m−1)
$\mathbf {\hat {k}}$ Cartesian z-axis basis unit vector unitless
$L$ inductance henry (H)
luminosity watt (W)
angular momentum newton meter second (N⋅m⋅s or kg⋅m2⋅s−1)
Lagrangian joule (J)
$l$ length meter (m)
azimuthal quantum number unitless
$M$ magnetization ampere per meter (A/m)
moment of force
often simply called moment or torque
newton meter (N⋅m)
$m$ mass kilogram (kg)
$N$ normal vector unit varies depending on context
atomic number unitless
$n$ refractive index unitless
principal quantum number unitless
amount of substance mole
$P$ power watt (W)
probability unitless
$\mathbf {p}$ momentum kilogram meter per second (kg⋅m/s)
pressure pascal (Pa)
$Q$ electric charge coulomb (C)
Heat joule (J)
$q$ electric charge coulomb (C)
$R$ electrical resistance ohm (Ω)
Ricci tensor
gas constant joule per mole per kelvin (J⋅mol−1⋅K−1)
$\mathbf {r}$ radius vector (position) meter (m)
$r$ radius or distance meter (m)
$S$ surface area m2
entropy joule per kelvin (J/K)
action joule second (J⋅s)
$s$ arc length meter (m)
displacement meter (m)
$T$ period second (s)
temperature kelvin (K) or Celsius (C)
$t$ time second (s)
$\mathbf {U}$ four-velocity meter per second (m/s)
$U$ potential energy joule (J)
internal energy joule (J)
$u$ relativistic mass kilogram (kg)
energy density joule per cubic meter (J/m3) or joule per kilogram (J/kg) depending on the context
$V$ voltage
also called electric potential difference
volt (V)
volume cubic meter (m3)
shear force
$\mathbf {v}$ velocity meter per second (m/s)
$W$ mechanical work joule (J)
$w$ width meter (m)
$x$ a generic unknown varied depending on context
displacement meter (m)
$Z$ electrical impedance ohm (Ω)

Greek characters

Symbol Name Meaning SI unit of measure
$\alpha$ alpha angular acceleration radian per second squared (rad/s2)
fine-structure constant unitless
$\beta$ beta velocity in terms of the speed of light c unitless
$\gamma$ gamma Lorentz factor unitless
photon
gamma ray
shear strain
heat capacity ratio unitless
$\Delta$ delta change in a variable (e.g. $\Delta x$ ) unitless
Laplace operator per square meter (m−2)
$\delta$ displacement (usually small) meter (m)
Dirac delta function
$\epsilon$ epsilon permittivity farad per meter (F/m)
strain unitless
$\varepsilon _{0}$ epsilon nought vacuum permittivity constant
$\zeta$ zeta damping ratio unitless
$\eta$ eta energy efficiency unitless
coefficient of viscosity
also called simply viscosity
pascal second (Pa⋅s)
jerk meter per second cubed (m/s3)
$\theta$ theta angular displacement radian (rad)
$\mathrm {K}$ kappa torsion coefficient
also called torsion constant
$\Lambda$ lambda cosmological constant per second squared (s−2)
$\lambda$ wavelength meter (m)
eigenvalue non-zero vector
fuel to oxidizer ratio in rocket fuel
$\mathbf {\mu }$ mu magnetic moment ampere square meter (A⋅m2)
coefficient of friction unitless
dynamic viscosity pascal second (Pa⋅s)
permeability (electromagnetism) henry per meter (H/m)
reduced mass kilogram (kg)
gravitational parameter
$\mathbf {\mu } _{0}$ mu nought vacuum permeability constant
$\nu$ nu frequency hertz (Hz)
kinematic viscosity meters squared per second (m2/s)
$\pi$ pi 3.14159... (irrational number) unitless
$\rho$ rho mass density
usually simply called density
kilogram per cubic meter (kg/m3)
volume charge density coulomb per cubic meter (C/m3)
resistivity ohm meter (Ω⋅m)
$\Sigma$ sigma summation operator
$\sigma$ electrical conductivity siemens per meter (S/m)
normal stress pascal (Pa)
$\tau$ tau torque newton meter (N⋅m)
shear stress pascal (Pa)
time constant second (s)
6.28318... () unitless
$\Phi$ phi field strength unit varies depending on context
magnetic flux weber (Wb)
$\phi$ electric potential volt (V)
Higgs field work function
$\Psi$ psi wave function m−3/2
$\Omega$ omega electric resistance ohm
$\omega$ angular frequency radian per second (rad/s)

Other characters

Symbol Name Meaning SI unit of measure
$\nabla \cdot$ nabla dot the divergence operator
often pronounced "del dot"
per meter (m−1)
$\nabla \times$ nabla cross the curl operator
often pronounced "del cross"
per meter (m−1)
$\nabla$ nabla delta (differential operator)
$\partial$ "der", "dow", "die", "partial" or simply "d" partial derivative (e.g. $\partial y/\partial x$ )
$\Box$ D'Alembert operator $\nabla ^{2}-\partial _{t}^{2}$ 