# 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
${\displaystyle \mathbf {A} }$ magnetic vector potential tesla meter (T⋅m)
${\displaystyle A}$ area square meters (m2)
amplitude meter
atomic mass number unitless
${\displaystyle \mathbf {a} }$ 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)
constant of integration varied depending on context
${\displaystyle c}$ speed of light (in vacuum) 299,792,458 meters per second (m/s)
speed of sound meters 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)
${\displaystyle \mathbf {D} }$ electric displacement field
also called the electric flux density
coulomb per square meter (C/m2)
${\displaystyle D}$ density kilograms per cubic meter (kg/m3)
diameter meter (m)
${\displaystyle d}$ distance meter (m)
direction unitless
impact parameter meter (m)
differential (e.g. ${\displaystyle dx}$) varied depending on context
${\displaystyle d\mathbf {A} }$ 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)
${\displaystyle e}$ eccentricity unitless
2.71828... (base of the natural logarithm) unitless
electron unitless
elementary charge coulomb (C)
${\displaystyle \mathbf {F} }$ force newton (N)
${\displaystyle F}$ Faraday constant coulombs per mole (C⋅mol−1)
${\displaystyle f}$ frequency hertz (Hz)
function
friction newton (N)
${\displaystyle G}$ electrical conductance siemens (S)
universal gravitational constant newton meter squared per kilogram squared (N⋅m2/kg2)
shear modulus pascal (Pa) or newton per square meter (N/m2)
${\displaystyle \mathbf {g} }$ acceleration due to gravity meters per second squared (m/s2), or equivalently, newtons per kilogram (N/kg)
${\displaystyle \mathbf {H} }$ magnetic field strength ampere per meter (A/m)
${\displaystyle H}$ Hamiltonian joule (J)
enthalpy joule (J)
${\displaystyle h}$ height meter (m)
Planck constant joule second (J⋅s)
${\displaystyle \hbar }$ reduced Planck constant 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 unitless
electric current ampere (A)
${\displaystyle \mathbf {\hat {\imath }} }$ Cartesian x-axis basis unit vector unitless
${\displaystyle \mathbf {J} }$ current density ampere per square meter (A/m2)
impulse kilogram meter per second (kg⋅m/s)
${\displaystyle \mathbf {j} }$ jerk meters per second cubed (m/s3)
${\displaystyle j}$ imaginary unit (electrical) unitless
${\displaystyle \mathbf {\hat {\jmath }} }$ Cartesian y-axis basis unit vector unitless
${\displaystyle K}$ kinetic energy joule (J)
${\displaystyle \mathbf {k} }$ wave vector radians per meter (m−1)
${\displaystyle k}$ Boltzmann constant joule per kelvin (J/K)
stiffness newtons per meter (N⋅m−1)
${\displaystyle \mathbf {\hat {k}} }$ Cartesian z-axis basis unit vector unitless
${\displaystyle \mathbf {L} }$ angular momentum newton meter second (N⋅m⋅s or kg⋅m2⋅s−1)
${\displaystyle L}$ inductance henry (H)
luminosity watt (W)
Lagrangian joule (J)
${\displaystyle l}$ length meter (m)
azimuthal quantum number unitless
${\displaystyle \mathbf {M} }$ magnetization amperes per meter (A/m)
${\displaystyle M}$ moment of force
often simply called moment or torque
newton meter (N⋅m)
${\displaystyle m}$ mass kilogram (kg)
${\displaystyle \mathbf {N} }$ normal vector unit varies depending on context
${\displaystyle N}$ atomic number unitless
${\displaystyle n}$ refractive index unitless
principal quantum number unitless
amount of substance mole
${\displaystyle P}$ power watt (W)
probability unitless
${\displaystyle \mathbf {p} }$ momentum kilogram meter per second (kg⋅m/s)
${\displaystyle p}$ 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 reciprocal square meter (m−2)
gas constant joule per mole per kelvin (J⋅mol−1⋅K−1)
${\displaystyle \mathbf {r} }$ radius vector (position) meter (m)
${\displaystyle r}$ radius or distance meter (m)
${\displaystyle S}$ surface area m2
entropy joule per kelvin (J/K)
action joule second (J⋅s)
${\displaystyle \mathbf {s} }$ displacement meter (m)
${\displaystyle s}$ arc length meter (m)
distance meter (m)
${\displaystyle T}$ period second (s)
temperature kelvin (K) or Celsius (C)
kinetic energy joule (J)
${\displaystyle t}$ 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)
specific energy joule per kilogram (J/kg)
${\displaystyle V}$ voltage
also called electric potential difference
volt (V)
volume cubic meter (m3)
shear force
${\displaystyle \mathbf {v} }$ velocity meter per second (m/s)
${\displaystyle W}$ weight newton (N)
mechanical work joule (J)
${\displaystyle w}$ width meter (m)
${\displaystyle X}$ electrical reactance ohm (Ω)
${\displaystyle \mathbf {x} }$ position vector meter (m)
displacement meter (m)
${\displaystyle x}$ a generic unknown varied depending on context
${\displaystyle Y}$ admittance siemens (S)
${\displaystyle Z}$ compressibility factor unitless
electrical impedance ohm (Ω)
${\displaystyle Z_{0}}$ impedance of free space ohm (Ω)

## Greek characters

Symbol Name Meaning SI unit of measure
${\displaystyle \alpha }$ alpha alpha particle
fine-structure constant unitless
${\displaystyle \beta }$ beta velocity in terms of the speed of light c unitless
beta particle
${\displaystyle \gamma }$ gamma Lorentz factor unitless
photon
gamma ray
heat capacity ratio unitless
surface tension newton per meter (N/m)
${\displaystyle \Delta }$ delta change in a variable (e.g. ${\displaystyle \Delta x}$) unitless
Laplace operator per square meter (m−2)
${\displaystyle \delta }$ displacement (usually small) meter (m)
Dirac delta function
Kronecker delta (e.g ${\displaystyle \delta _{ij}}$)
${\displaystyle \epsilon }$ epsilon permittivity farad per meter (F/m)
strain unitless
${\displaystyle \varepsilon _{0}}$ epsilon nought vacuum permittivity constant farad per meter (F/m)
${\displaystyle \zeta }$ zeta damping ratio unitless
${\displaystyle \eta }$ eta angular jerk radians per second cubed (rad⋅s−3)
energy efficiency unitless
(dynamic) viscosity (also ${\displaystyle \mu }$) pascal second (Pa⋅s)
${\displaystyle \theta }$ theta angular displacement radian (rad)
${\displaystyle \kappa }$ kappa torsion coefficient
also called torsion constant
${\displaystyle \Lambda }$ lambda cosmological constant per second squared (s−2)
${\displaystyle \lambda }$ wavelength meter (m)
linear charge density coulomb per meter (C/m)
eigenvalue non-zero vector
${\displaystyle \mathbf {\mu } }$ mu magnetic moment ampere square meter (A⋅m2)
coefficient of friction unitless
(dynamic) viscosity (also ${\displaystyle \eta }$) pascal second (Pa⋅s)
permeability (electromagnetism) henry per meter (H/m)
reduced mass kilogram (kg)
gravitational parameter cubic meter per second squared
${\displaystyle \mathbf {\mu } _{0}}$ mu nought vacuum permeability constant or magnetic constant henry per meter (H/m)
${\displaystyle \nu }$ nu frequency hertz (Hz)
kinematic viscosity meters squared per second (m2/s)
neutrino
${\displaystyle \xi }$ xi electromotive force volt (V)
${\displaystyle \pi }$ pi 3.14159... (irrational number) unitless
${\displaystyle \rho }$ 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)
${\displaystyle \Sigma }$ sigma summation operator
${\displaystyle \sigma }$ area charge density coulomb per square meter (C/m2)
electrical conductivity siemens per meter (S/m)
normal stress pascal (Pa)
scattering cross section barn (10^-28 m^2)
surface tension newton per meter (N/m)
${\displaystyle \tau }$ tau torque newton meter (N⋅m)
shear stress pascal (Pa)
time constant second (s)
6.28318... () unitless
${\displaystyle \Phi }$ phi field strength unit varies depending on context
magnetic flux weber (Wb)
${\displaystyle \phi }$ electric potential volt (V)
Higgs field work function
${\displaystyle \Psi }$ psi wave function m−3/2
${\displaystyle \Omega }$ omega electric resistance ohm
${\displaystyle \omega }$ angular frequency radian per second (rad/s)

## 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)
${\displaystyle \partial }$ "der", "dow", "die", "partial" or simply "d" partial derivative (e.g. ${\displaystyle \partial y/\partial x}$)
${\displaystyle \Box }$ D'Alembert operator ${\displaystyle \nabla ^{2}-\partial _{t}^{2}}$
${\displaystyle \langle \,\,\rangle }$ angle brackets average

sometimes over Maxwell–Boltzmann distribution

${\displaystyle \langle \ |\ \rangle }$ Dirac notation