Physical notations

Physical notations

Symbol	Meaning	SI unit of measure
${\displaystyle A}$	area	meter squared (m2)
	magnetic vector potential
	amplitude	meter
${\displaystyle \mathbf {a} }$	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 kilogramper 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)
${\displaystyle e}$	eccentricity	unitless
	2.71828... (base of the natural logarithm), electron, elementary charge
${\displaystyle \mathbf {F} }$	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 also called just magnetic field	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
${\displaystyle \mathbf {J} }$	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)
${\displaystyle \mathbf {\hat {j}} }$	Cartesian y-axis basis unit vector	unitless
${\displaystyle K}$	kinetic energy	joule (J)
${\displaystyle k}$	Boltzmann constant	joule per kelvin (J/K)
	wavenumber	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)
${\displaystyle l}$	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
	radiancy
	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
${\displaystyle T}$	period	second (s)
	thermodynamic temperature also called absolute 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[edit]

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 (e.g. ${\displaystyle \Delta x}$)	unitless
		Laplace operator
${\displaystyle \delta }$	delta	displacement (usually small)
${\displaystyle \epsilon }$	epsilon	permittivity	farad per meter (F/m)
		strain	unitless
${\displaystyle \zeta }$	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	newton meter per radian (N m/rad)
${\displaystyle \Lambda }$	lambda	cosmological constant	per second squared (s−2)
${\displaystyle \lambda }$		wavelength	meter (m)
${\displaystyle \mathbf {\mu } }$	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)
${\displaystyle \nu }$	nu	frequency	hertz (Hz)
		kinematic viscosity	meters squared per second (m2/s)
${\displaystyle \pi }$	pi	3.14159... (irrational number)
${\displaystyle \rho }$	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... (2π)
${\displaystyle \Phi }$	phi	field strength	unit varies depending on context
		magnetic flux	Weber (Wb)
${\displaystyle \phi }$	phi	electric potential Higgs Field
${\displaystyle \Psi }$	psi	wave function	unitless
${\displaystyle \omega }$	omega	angular frequency	radian per second (rad/s)
${\displaystyle \Omega }$	omega	electric resistance	ohm