# 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
${\displaystyle A}$ area meter squared (m2)
magnetic vector potential
amplitude meter
atomic mass number
${\displaystyle \mathbf {a} }$ acceleration meters per second squared (m/s2)
${\displaystyle \mathbf {B} }$ magnetic flux density
also called the magnetic field density or magnetic induction
tesla (T), or equivalently,
weber per square meter (Wb/m2)
${\displaystyle C}$ capacitance farad (F)
heat capacity joule per kelvin (J K−1), or equivalently, joule per degree Celsius (J °C−1)
constant of integration varied depending on context
${\displaystyle c}$ 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), or equivalently, joule per kilogram per degree Celsius (J kg−1 °C−1)
viscous damping coefficient kilogram per second (kg/s)
${\displaystyle \mathbf {D} }$ electric displacement field
also called the electric flux density
coulomb per square meter (C/m2)
${\displaystyle D}$ density kilograms per cubic meter (kg/m3)
${\displaystyle d}$ distance meter (m)
direction unitless
impact parameter meter (m)
diameter meter (m)
differential (e.g. ${\displaystyle dx}$)
${\displaystyle d\mathbf {A} }$ differential vector element of surface area A, with infinitesimally

small magnitude and direction normal to surface S

square meter (m2)
${\displaystyle dV}$ differential element of volume V enclosed by surface S cubic meter (m3)
${\displaystyle \mathbf {E} }$ electric field newton per coulomb (N C−1), or equivalently, volt per meter (V m−1)
${\displaystyle E}$ energy joule (J)
Young's Modulus Pascal (Pa) or Newton per square meter (N/m2) or kilogram per meter per second squared (kg·m−1·s−2)
${\displaystyle e}$ eccentricity unitless
2.71828... (base of the natural logarithm) unitless
elementary charge coulomb (C)
electron 9.10938×10−31(kg)
${\displaystyle \mathbf {F} }$ force newton (N)
${\displaystyle f}$ frequency hertz (Hz)
function
friction newton (N)
${\displaystyle G}$ the gravitational constant newton meter squared per kilogram squared (N m2/kg2)
${\displaystyle g}$ acceleration due to gravity meter per second squared (m/s2), or equivalently, newton per kilogramme (N/kg)
${\displaystyle \mathbf {H} }$ magnetic field strength ampere per meter (A/m)
${\displaystyle H}$ Hamiltonian joule (J)
${\displaystyle h}$ height meter (m)
Planck's constant joule second (J s)
${\displaystyle \hbar }$ reduced Planck's constant ${\displaystyle \textstyle \left({\frac {h}{2\pi }}\right)}$ joule second (J s)
${\displaystyle I}$ 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)
${\displaystyle i}$ intensity watt per square meter (W/m2)
imaginary unit
${\displaystyle \mathbf {\hat {i}} }$ Cartesian x-axis basis unit vector unitless
${\displaystyle j}$ imaginary unit (electrical)
${\displaystyle \mathbf {J} }$ 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)
${\displaystyle \mathbf {\hat {j}} }$ Cartesian y-axis basis unit vector unitless
${\displaystyle K}$ kinetic energy joule (J)
${\displaystyle k}$ Boltzmann constant joule per kelvin (J/K)
wavenumber, wave vector radians per meter (m−1)
${\displaystyle \mathbf {\hat {k}} }$ Cartesian z-axis basis unit vector unitless
${\displaystyle L}$ inductance henry (H)
luminosity watt (W)
angular momentum newton meter second (N m s or kg m2 s−1)
Lagrangian joule (J)
${\displaystyle l}$ length meter (m)
${\displaystyle M}$ magnetization ampere per meter (A/m)
moment of force
often simply called moment or torque
newton meter (N m)
${\displaystyle m}$ mass kilogram (kg)
${\displaystyle N}$ normal vector unit varies depending on context
atomic number unitless
${\displaystyle n}$ refractive index unitless
principal quantum number unitless
${\displaystyle P}$ power watt (W)
${\displaystyle \mathbf {p} }$ momentum kilogram meter per second (kg m/s)
pressure pascal (Pa)
${\displaystyle Q}$ electric charge coulomb (C)
Heat joule (J)
${\displaystyle q}$ electric charge coulomb (C)
${\displaystyle R}$ electrical resistance ohm (Ω)
Ricci tensor unitless
gas constant joule per kilogramme kelvin (J/kgK)
${\displaystyle \mathbf {r} }$ radius vector (position) meter (m)
${\displaystyle r}$ radius of rotation or distance between two things such as the masses in Newton's law of universal gravitation meter (m)
${\displaystyle S}$ surface area m2
entropy joule per kelvin (J/K)
action
${\displaystyle s}$ arc length meter (m)
displacement meter (m)
${\displaystyle T}$ period second (s)
temperature kelvin (K)
${\displaystyle t}$ time second (s)
${\displaystyle \mathbf {U} }$ four-velocity meter per second (m/s)
${\displaystyle U}$ potential energy joule (J)
internal energy joule (J)
${\displaystyle u}$ relativistic mass kilogram (kg)
energy density joule per cubic meter (J/m3) or joule per kilogram (J/kg) depending on the context
${\displaystyle V}$ voltage
also called electric potential difference
volt (V)
volume cubic meter (m3)
shear force
${\displaystyle \mathbf {v} }$ velocity meter per second (m/s)
${\displaystyle W}$ mechanical work joule (J)
${\displaystyle w}$ width meter (m)
${\displaystyle x}$ a generic unknown varied depending on context
displacement meter (m)
${\displaystyle Z}$ electrical impedance ohm (Ω)

## Greek characters

Symbol Name Meaning SI unit of measure
${\displaystyle \alpha }$ alpha angular acceleration radian per second squared (rad/s2)
${\displaystyle \beta }$ beta velocity in terms of the speed of light c unitless
${\displaystyle \gamma }$ gamma Lorentz factor unitless
photon
gamma ray
shear strain
Heat capacity ratio unitless
${\displaystyle \Delta }$ delta a change in a variable (a change of "blank") (e.g. ${\displaystyle \Delta x}$) unitless
Laplace operator per square meter (m−2)
${\displaystyle \delta }$ displacement (usually small)
${\displaystyle \epsilon }$ epsilon permittivity farad per meter (F/m)
strain unitless
${\displaystyle \varepsilon _{0}}$ epsilon

nought

The vacuum permittivity constant
${\displaystyle \zeta }$ zeta damping ratio unitless
${\displaystyle \eta }$ eta energy efficiency unitless
coefficient of viscosity
also called simply viscosity
pascal second (Pa s)
${\displaystyle \theta }$ theta angular displacement radian (rad)
${\displaystyle \mathrm {K} }$ kappa torsion coefficient
also called torsion constant
${\displaystyle \Lambda }$ lambda cosmological constant per second squared (s−2)
${\displaystyle \lambda }$ wavelength meter (m)
eigenvalue non-zero vector
${\displaystyle \mathbf {\mu } }$ 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
${\displaystyle \nu }$ nu frequency hertz (Hz)
kinematic viscosity meters squared per second (m2/s)
${\displaystyle \pi }$ pi 3.14159... (irrational number) unitless
${\displaystyle \rho }$ rho mass density
usually simply called density
kilogram per cubic meter (kg/m3)
free electric charge density,
not including dipole charges bound in a material
coulomb per cubic meter (C/m3)
resistivity Ohm meter (${\displaystyle \Omega }$ m)
${\displaystyle \Sigma }$ sigma summation operator
${\displaystyle \sigma }$ sigma electrical conductivity Siemens per meter (S/m)
normal stress
${\displaystyle \tau }$ tau torque newton meter (N m)
shear stress
time constant second (s)
6.28318... () unitless
${\displaystyle \Phi }$ phi field strength unit varies depending on context
Magnetic Flux Weber (Wb)
${\displaystyle \phi }$ phi Electric Potential volt (V)
Higgs Field Work Function
${\displaystyle \Psi }$ psi Wave function m−3/2
${\displaystyle \omega }$ omega Angular frequency

2πf

${\displaystyle \Omega }$ omega electric resistance ohm
η Eta Jerk meter per second cubed (m/s3)

## Other characters

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