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 meter (m2)
	amplitude	meter
	atomic mass number	unitless
${\displaystyle \mathbf {a} }$	acceleration	meter 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	meter 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	kilogram 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)
	thermal current	watt (W)
${\displaystyle h}$	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	meter 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	radian per meter (m−1)
${\displaystyle k}$	Boltzmann constant	joule per kelvin (J/K)
	wavenumber	radian per meter (m−1)
	stiffness	newton 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)
${\displaystyle {\mathcal {L))}$	Lagrangian density	joule per cubic meter (J/m3)
${\displaystyle l}$	length	meter (m)
ℓ	azimuthal quantum number	unitless
${\displaystyle \mathbf {M} }$	magnetization	ampere 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)
	radiancy	meter per second
	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	square meter (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
		angular acceleration	radian per second squared (rad/s2)
		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
		shear strain	radian
		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	farad per meter (F/m)
${\displaystyle \zeta }$	zeta	damping ratio	unitless
${\displaystyle \eta }$	eta	angular jerk	radian 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	newton meter per radian (N⋅m/rad)
${\displaystyle \Lambda }$	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)
		Standard gravitational parameter	cubic meter per second squared
${\displaystyle \mathbf {\mu } _{0))$	mu nought	Vacuum permeability or the magnetic constant	henry per meter (H/m)
${\displaystyle \nu }$	nu	frequency	hertz (Hz)
		kinematic viscosity	meter 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... (2π)	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)
		angular velocity	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
${\displaystyle \int }$	integral	the inverse of the derivative.	unitless