List of common physics notations explained

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	magnetic vector potential	tesla meter (T⋅m)
A	area	square meter (m2)
amplitude	meter
atomic mass number	unitless
a	acceleration	meter per second squared (m/s2)
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)
constant of integration	varied depending on context
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)
D	electric displacement field also called the electric flux density	coulomb per square meter (C/m2)
D	density	kilogram per cubic meter (kg/m3)
diameter	meter (m)
d	distance	meter (m)
direction	unitless
impact parameter	meter (m)
differential (e.g. dx )	varied depending on context
dA	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)
E	electric field	newton per coulomb (N⋅C−1), or equivalently, volt per meter (V⋅m−1)
E	energy	joule (J)
Young's modulus	pascal (Pa) or newton per square meter (N/m2)
e	eccentricity	unitless
2.71828... (base of the natural logarithm)	unitless
electron	unitless
elementary charge	coulomb (C)
F	force	newton (N)
F	Faraday constant	coulombs per mole (C⋅mol−1)
f	frequency	hertz (Hz)
function
friction	newton (N)
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)
g	acceleration due to gravity	meters per second squared (m/s2), or equivalently, newtons per kilogram (N/kg)
H	magnetic field strength	ampere per meter (A/m)
H	Hamiltonian	joule (J)
	enthalpy	joule (J)
	thermal current	watt (W)
h	height	meter (m)
	Planck constant	joule second (J⋅s)
\hbar	reduced Planck constant	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	unitless
electric current	ampere (A)
\hat{\imath }	Cartesian x-axis basis unit vector	unitless
J	current density	ampere per square meter (A/m2)
impulse	kilogram meter per second (kg⋅m/s)
j	jerk	meter per second cubed (m/s3)
j	imaginary unit (electrical)	unitless
\hat{\jmath }	Cartesian y-axis basis unit vector	unitless
K	kinetic energy	joule (J)
k	wave vector	radian per meter (m−1)
k	Boltzmann constant	joule per kelvin (J/K)
wavenumber	radian per meter (m−1)
stiffness	newton per meter (N⋅m−1)
\hat{k }	Cartesian z-axis basis unit vector	unitless
L	angular momentum	newton meter second (N⋅m⋅s or kg⋅m2⋅s−1)
L	inductance	henry (H)
luminosity	watt (W)
Lagrangian	joule (J)
l{L}	Lagrangian density	joule per cubic meter (J/m3)
l	length	meter (m)
ℓ	azimuthal quantum number	unitless
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)
N	normal vector	unit varies depending on context
N	atomic number	unitless
n	refractive index	unitless
principal quantum number	unitless
amount of substance	mole
P	power	watt (W)
probability	unitless
p	momentum	kilogram meter per second (kg⋅m/s)
p	pressure	pascal (Pa)
Q	electric charge	coulomb (C)
heat	joule (J)
q	electric charge	coulomb (C)
R	electrical resistance	ohm (Ω)
Ricci tensor	reciprocal square meter (m−2)
radiancy
gas constant	joule per mole per kelvin (J⋅mol−1⋅K−1)
r	radius vector (position)	meter (m)
r	radius or distance	meter (m)
S	surface area	square meter (m2)
entropy	joule per kelvin (J/K)
action	joule second (J⋅s)
s	displacement	meter (m)
s	arc length	meter (m)
distance	meter (m)
T	period	second (s)
temperature	kelvin (K) or Celsius (C)
kinetic energy	joule (J)
t	time	second (s)
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)
specific energy	joule per kilogram (J/kg)
V	voltage also called electric potential difference	volt (V)
volume	cubic meter (m3)
shear force
v	velocity	meter per second (m/s)
W	weight	newton (N)
mechanical work	joule (J)
w	width	meter (m)
X	electrical reactance	ohm (Ω)
x	position vector	meter (m)
displacement	meter (m)
x	a generic unknown	varied depending on context
Y	admittance	siemens (S)
Z	compressibility factor	unitless
electrical impedance	ohm (Ω)
Z0	impedance of free space	ohm (Ω)

Greek characters

Symbol	Name	Meaning	SI unit of measure
\alpha	alpha	alpha particle
angular acceleration	radian per second squared (rad/s2)
fine-structure constant	unitless
\beta	beta	velocity in terms of the speed of light c	unitless
beta particle
\gamma	gamma	Lorentz factor	unitless
photon
gamma ray
shear strain	radian
heat capacity ratio	unitless
surface tension	newton per meter (N/m)
\Delta	delta	change in a variable (e.g. \Deltax )	unitless
Laplace operator		per square meter (m−2)
\delta		displacement (usually small)	meter (m)
		Dirac delta function
		Kronecker delta (e.g \deltaij )
\epsilon	epsilon	permittivity	farad per meter (F/m)
		strain	unitless
\varepsilon0	epsilon nought	Vacuum permittivity	farad per meter (F/m)
\zeta	zeta	damping ratio	unitless
η	eta	angular jerk	radian per second cubed (rad⋅s−3)
energy efficiency	unitless
(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)
Λ	lambda	cosmological constant	per second squared (s−2)
λ	wavelength	meter (m)
	linear charge density	coulomb per meter (C/m)
	eigenvalue	non-zero vector
\mu	mu	magnetic moment	ampere square meter (A⋅m2)
		coefficient of friction	unitless
		(dynamic) viscosity (also η )	pascal second (Pa⋅s)
		permeability (electromagnetism)	henry per meter (H/m)
		reduced mass	kilogram (kg)
		Standard gravitational parameter	cubic meter per second squared
\mu0	mu nought	Vacuum permeability or the magnetic constant	henry per meter (H/m)
\nu	nu	frequency	hertz (Hz)
kinematic viscosity	meter squared per second (m2/s)
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/m3)
volume charge density	coulomb per cubic meter (C/m3)
resistivity	ohm meter (Ω⋅m)
\Sigma	sigma	summation operator
\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)
\tau	tau	torque	newton meter (N⋅m)
shear stress	pascal (Pa)
time constant	second (s)
6.28318... (2π)	unitless
\Phi	phi	field strength	unit varies depending on context
magnetic flux	weber (Wb)
\phi	electric potential	volt (V)
Higgs field work function
\Psi	psi	wave function	m−3/2
\Omega	omega	electric resistance	ohm
\omega		angular frequency	radian per second (rad/s)
		angular velocity	radian per second (rad/s)

Other characters

Symbol	Name	Meaning	SI unit of measure
\nabla ⋅	nabla dot	the divergence operator often pronounced "del dot"	per meter (m−1)
\nabla x	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. \partialy/\partialx )
\Box	D'Alembert operator	2 \nabla t
\langle\rangle	angle brackets
\langle	\ \rangle	Dirac notation
\int	integral	the inverse of the derivative.	unitless

See also

• List of letters used in mathematics and science
• Glossary of mathematical symbols
• List of mathematical uses of Latin letters
• Greek letters used in mathematics, science, and engineering
• Physical constant
• Physical quantity
• International System of Units
• ISO 31

References

• Web site: Elert. Glenn. Special Symbols. The Physics Hypertextbook. 4 August 2021.
• Web site: NIST. SI Units. 16 August 2023. www.nist.gov. NIST.