VARIOUS PHYSICS SYMBOLS , MEANINGS AND UNITS

Symbol	Meaning	SI unit of measure
$A$	area	meter squared (m²)
	magnetic vector potential
	amplitude
$a$	acceleration	meter per second squared (m/s²) or (m s⁻²)
$\mathbf{B}$	magnetic flux intensity 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)
$d$	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
$e$	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)
$\mathbf{H}$	magnetic field strength also called just magnetic field	ampere per meter (A/m)
$H$	Hamiltonian	joule (J)
$h$	height	meter (m)
$h$	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)
$i$	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)
$\mathbf{J}$	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)
$k$	wave number	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)
$M$	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
$n$	principal quantum number	unitless
$P$	power	watt (W)
$\mathbf{p}$	momentum	kilogram meter per second (kg m/s)
$\mathbf{p}$	pressure	pascal (Pa)
$Q$	electric charge	coulomb (C)
$Q$	Heat	joule (J)
$q$	electric charge	coulomb (C)
$R$	electrical resistance	ohm (Ω)
	Ricci tensor	unitless
	radiancy
$\mathbf{r}$	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)
$s$	displacement
$T$	period	second (s)
$T$	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)
$U$	internal energy	joule (J)
$u$	relativistic mass	kilogram (kg)
$u$	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
$x$	displacement	meter (m)
$Z$	electrical impedance	ohm (Ω)