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
$A$	area	meter squared (m2)
	magnetic vector potential
	amplitude
$\mathbf{a}$	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), or equivalently, joule per degree Celsius (J °C−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), or equivalently, joule per kilogram per degree Celsius (J kg−1 °C−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)
	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)
$e$	eccentricity	unitless
	2.71828... (base of the natural logarithm), electron, elementary charge
$\mathbf{F}$	force	newton (N)
$f$	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 kilogramme (N/kg)
$\mathbf{H}$	magnetic field strength also called just magnetic field	ampere per meter (A/m)
$H$	Hamiltonian	joule (J)
$h$	height	meter (m)
	Planck's constant	joule second (J s)
$\hbar$	reduced Planck's constant $\textstyle \left ( {\frac h {2\pi}}\right)$	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 polarization or magnetization currents bound in a material	ampere per square meter (A/m2)
	impulse	kilogram meter per second (kg m/s)
$\mathbf{\hat{j}}$	Cartesian y-axis basis unit vector	unitless
$K$	kinetic energy	joule (J)
$k$	Boltzmann constant	joule per kelvin (J/K)
	wavenumber	radians per meter (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)
$l$	length	meter (m)
$M$	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
$P$	power	watt (W)
$\mathbf{p}$	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	unitless
	radiancy
	gas constant	joule per kilogramme kelvin (J/kgK)
$\mathbf{r}$	radius vector (position)	meter (m)
$r$	radius of rotation or distance between two things such as the masses in Newton's law of universal gravitation	meter (m)
$S$	surface area	m2
	entropy	joule per kelvin (J/K)
	action
$s$	arc length	meter (m)
	displacement
$T$	period	second (s)
	thermodynamic temperature also called absolute temperature	kelvin (K)
$t$	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)
$\beta$	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	a change in a variable (e.g. $\Delta x$)	unitless
		Laplace operator
$\delta$	delta	displacement (usually small)
$\epsilon$	epsilon	permittivity	farad per meter (F/m)
		strain	unitless
$\zeta$	zeta	damping ratio	unitless
$\eta$	eta	energy efficiency	unitless
		coefficient of viscosity also called simply viscosity	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)
$\lambda$		wavelength	meter (m)
$\mathbf{\mu}$	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)
$\nu$	nu	frequency	hertz (Hz)
		kinematic viscosity	meters squared per second (m2/s)
$\pi$	pi	3.14159... (irrational number)
$\rho$	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 ($\Omega$ m)
$\Sigma$	sigma	summation operator
$\sigma$	sigma	electrical conductivity	Siemens per meter (S/m)
		normal stress
$\tau$	tau	torque	newton meter (N m)
		shear stress
		time constant	second (s)
		6.28318... (2π)
$\Phi$	phi	field strength	unit varies depending on context
		magnetic flux	Weber (Wb)
$\phi$	phi	electric potential Higgs Field
$\Psi$	psi	wave function	unitless
$\omega$	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	del (differential operator)
$\part$	"der", "dow", "die", "partial" or simply "d"	partial derivative (e.g. $\part y/\part x$)
$\Box$	D'Alembert operator	$\nabla^2-\part_t^2$

See also

• List of letters used in mathematics and science
• Roman letters used in mathematics
• Greek letters used in mathematics, science, and engineering
• Physical constant
• Physical quantity
• International System of Units
• ISO 31