# 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 | tesla meter (T⋅m) |
| $A$ | area | square meter (m$^2$) |
| $A$ | amplitude | meter |
| $A$ | atomic mass number | unitless |
| $\mathbf {a}$ | acceleration | meter per second squared (m/s$^2$) |
| $\mathbf {B}$ | magnetic flux density also called the magnetic field density or magnetic induction | tesla (T), or equivalently, weber per square meter (Wb/m$^2$) |
| $C$ | capacitance | farad (F) |
| $C$ | heat capacity | joule per kelvin (J⋅K$^{−1}$) |
| $C$ | constant of integration | varied depending on context |
| $c$ | speed of light (in vacuum) | 299,792,458 meters per second (m/s) |
| $c$ | speed of sound | meter per second (m/s) |
| $c$ | specific heat capacity | joule per kilogram per kelvin (J⋅kg$^{−1}$⋅K$^{−1}$) |
| $c$ | viscous damping coefficient | kilogram per second (kg/s) |
| $\mathbf {D}$ | electric displacement field also called the electric flux density | coulomb per square meter (C/m$^2$) |
| $D$ | density | kilogram per cubic meter (kg/m$^3$) |
| $D$ | diameter | meter (m) |
| $d$ | distance | meter (m) |
| $d$ | direction | unitless |
| $d$ | impact parameter | meter (m) |
| $d$ | differential (e.g. $dx$) | varied depending on context |
| $d\mathbf {A}$ | differential vector element of surface area A, with infinitesimally small magnitude and direction normal to surface S | square meter (m$^2$) |
| $dV$ | differential element of volume V enclosed by surface S | cubic meter (m$^3$) |
| $\mathbf {E}$ | electric field | newton per coulomb (N⋅C$^{−1}$), or equivalently, volt per meter (V⋅m$^{−1}$) |
| $E$ | energy | joule (J) |
| $E$ | Young's modulus | pascal (Pa) or newton per square meter (N/m$^2$) |
| $e$ | eccentricity | unitless |
| $e$ | Euler's number (2.71828, base of the natural logarithm) | unitless |
| $e$ | electron | unitless |
| $e$ | elementary charge | coulomb (C) |
| $\mathbf {F}$ | force | newton (N) |
| $F$ | Faraday constant | coulombs per mole (C⋅mol$^{−1}$) |
| $f$ | frequency | hertz (Hz) |
| $f$ | function | |
| $f$ | friction | newton (N) |
| $G$ | electrical conductance | siemens (S) |
| $G$ | universal gravitational constant | newton meter squared per kilogram squared (N⋅m$^2$/kg$^2$) |
| $G$ | shear modulus | pascal (Pa) or newton per square meter (N/m$^2$) |
| $G$ | gluon field strength tensor | inverse length squared (1/m$^2$) |
| $\mathbf {g}$ | acceleration due to gravity | meters per second squared (m/s$^2$), or equivalently, newtons per kilogram (N/kg) |
| $\mathbf {H}$ | magnetic field strength | ampere per meter (A/m) |
| $H$ | Hamiltonian | joule (J) |
| $H$ | enthalpy | joule (J) |
| $H$ | thermal current | watt (W) |
| $h$ | height | meter (m) |
| $h$ | Planck constant | joule second (J⋅s) |
| $\hbar$ | reduced Planck constant | joule second (J⋅s) |
| $I$ | action | joule second (J⋅s) |
| $I$ | intensity | watt per square meter (W/m$^2$) |
| $I$ | sound intensity | watt per square meter (W/m$^2$) |
| $I$ | electric current | ampere (A) |
| $I$ | moment of inertia | kilogram meter squared (kg⋅m$^2$) |
| $i$ | intensity | watt per square meter (W/m$^2$) |
| $i$ | imaginary unit | unitless |
| $i$ | electric current | ampere (A) |
| $\mathbf {\hat {\imath }}$ | Cartesian x-axis basis unit vector | unitless |
| $\mathbf {J}$ | current density | ampere per square meter (A/m$^2$) |
| $\mathbf {J}$ | impulse | kilogram meter per second (kg⋅m/s) |
| $\mathbf {j}$ | jerk | meter per second cubed (m/s$^3$) |
| $j$ | imaginary unit (electrical) | unitless |
| $\mathbf {\hat {\jmath }}$ | Cartesian y-axis basis unit vector | unitless |
| $K$ | kinetic energy | joule (J) |
| $\mathbf {k}$ | wave vector | radian per meter (m$^{−1}$) |
| $k$ | Boltzmann constant | joule per kelvin (J/K) |
| $k$ | wavenumber | radian per meter (m$^{−1}$) |
| $k$ | stiffness | newton per meter (N⋅m$^{−1}$) |
| $\mathbf {\hat {k}}$ | Cartesian z-axis basis unit vector | unitless |
| $\mathbf {L}$ | angular momentum | newton meter second (N⋅m⋅s or kg⋅m$^2$⋅s$^{−1}$) |
| $L$ | inductance | henry (H) |
| $L$ | luminosity | watt (W) |
| $L$ | Lagrangian | joule (J) |
| ${\mathcal {L}}$ | Lagrangian density | joule per cubic meter (J/m$^3$) |
| $l$ | length | meter (m) |
| ℓ | azimuthal quantum number | unitless |
| $\mathbf {M}$ | magnetization | ampere per meter (A/m) |
| $M$ | moment of force often simply called moment or torque | newton meter (N⋅m) |
| $m$ | mass | kilogram (kg) |
| $\mathbf {N}$ | normal vector | unit varies depending on context |
| $N$ | atomic number | unitless |
| $n$ | refractive index | unitless |
| $n$ | principal quantum number | unitless |
| $n$ | amount of substance | mole |
| $P$ | power | watt (W) |
| $P$ | active power (real power) | watt (W) |
| $P$ | probability | unitless |
| $\mathbf {p}$ | momentum | kilogram meter per second (kg⋅m/s) |
| $p$ | pressure | pascal (Pa) |
| $Q$ | electric charge | coulomb (C) |
| $Q$ | heat | joule (J) |
| $Q$ | Reactive Power | volt-ampere reactive (var) |
| $q$ | electric charge | coulomb (C) |
| $R$ | electrical resistance | ohm (Ω) |
| $R$ | Ricci tensor | reciprocal square meter (m$^{−2}$) |
| $R$ | radiancy | meter per second |
| $R$ | 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 | square meter (m$^2$) |
| $S$ | entropy | joule per kelvin (J/K) |
| $S$ | action | joule second (J⋅s) |
| $S$ | apparent power (complex power) | Volt-Ampere (VA) |
| $\mathbf {s}$ | displacement | meter (m) |
| $s$ | arc length | meter (m) |
| $s$ | distance | meter (m) |
| $T$ | period | second (s) |
| $T$ | temperature | kelvin (K) or Celsius (C) |
| $T$ | kinetic energy | joule (J) |
| $t$ | time | second (s) |
| $\mathbf {U}$ | four-velocity | meter per second (m/s) |
| $U$ | potential energy | joule (J) |
| $U$ | internal energy | joule (J) |
| $u$ | relativistic mass | kilogram (kg) |
| $u$ | energy density | joule per cubic meter (J/m$^3$) |
| $u$ | specific energy | joule per kilogram (J/kg) |
| $V$ | voltage also called electric potential difference | volt (V) |
| $V$ | volume | cubic meter (m$^3$) |
| $V$ | shear force | |
| $\mathbf {v}$ | velocity | meter per second (m/s) |
| $W$ | weight | newton (N) |
| $W$ | mechanical work | joule (J) |
| $w$ | width | meter (m) |
| $X$ | electrical reactance | ohm (Ω) |
| $\mathbf {x}$ | position vector | meter (m) |
| $\mathbf {x}$ | displacement | meter (m) |
| $x$ | a generic unknown | varied depending on context |
| $Y$ | admittance | siemens (S) |
| $Z$ | compressibility factor | unitless |
| $Z$ | electrical impedance | ohm (Ω) |
| $Z_{0}$ | impedance of free space | ohm (Ω) |

## Greek characters

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