Wikipedia:WikiProject Electronics/Standard symbols

Reference should be made to codes and standards. For example, IEC 60027, and Letter Symbols in Electrical Technology.

Here are tables of widely accepted symbols. They are meant to be a guideline: Using the same symbols for the same things in different articles will increase their consistency, making them easier to understand and to improve. If you are looking for the symbol for something that is not on the list, just check whether a particular symbol has been already chosen, and create your own. If anybody will disagree with it, discuss it on the talk page.

It is certainly not an exhaustive list, nor is it in any particular order.

Waves and waveforms

Symbol	Meaning	SI Units of Measure
$\ f\$	frequency	hertz (cycles per second)
$\ \omega \$	angular frequency	radians per second
$\ k\$	wave number	radians per meter
$\ \lambda \$	wavelength	meters per cycle
$\ T\$	period	seconds per cycle

Optics and photonics

Symbol	Meaning	SI Units of Measure
$\ n\$	refractive index	dimensionless
$\ c_{0}$	speed of light in vacuum	meters per second
$\ c\$	speed of light in material medium	meters per second
$\ \nu \$	frequency	hertz (cycles per second)
$\ \omega \$	angular frequency	radians per second
$\ k\$	wave number	radians per meter
$\ \lambda \$	wavelength	meters per cycle
$\ R\$	radius of curvature	meters
$\Gamma \$	reflection coefficient	dimensionless
$\alpha \$	absorption coefficient	dimensionless
${\mathcal {R}}\$	reflectivity	dimensionless
${\mathcal {T}}\$	transmissivity	dimensionless

Electromagnetics

Symbol	Meaning	SI Units of Measure
$\mathbf {E}$	Electric field	volts per meter
$\mathbf {H}$	Magnetic field	amperes per meter
$\mathbf {D}$	Electric displacement	coulombs per square meter
$\mathbf {B}$	Magnetic flux density	teslas or webers per square meter
$\Phi _{\mathbf {D} }$	Electric flux	voltmeters
$\Phi _{\mathbf {B} }$	Magnetic flux	webers
$\mathbf {P}$	Polarization density	coulombs per square meter
$\mathbf {M}$	Magnetization	amperes per meter
$\mathbf {J}$	Current density	amperes per square meter
$\ \varepsilon \$	Electric permittivity	farads per meter
$\ \mu \$	Magnetic permeability	henries per meter
$\ \sigma \$	conductivity	siemens per meter
$\ \chi \$	susceptibility	dimensionless
$\ q\$	Electric charge	coulombs
$\ \rho \$	Electric charge density	coulombs per cubic meter
$\ \Phi \$	Electric potential	volts
$\ \Psi \$	Magnetic scalar potential	amperes
$\mathbf {A}$	Magnetic vector potential	webers per meter

R} Resistance of " R"

Electrical circuits

Symbol	Meaning	SI Units of Measure
$\ B\$	Susceptance	siemens
$\ C\$	Capacitance	farad
$\ G\$	Conductance	siemens
$\ L\$	Inductance	henry
$\ i\$	Current	ampere
$\ I\$	Alternating Current	ampere
$\ P\$	Power	Watt
$\ Q\$	Reactive Power	Volt-Ampere Reactive
$\ R\$	Resistance	ohm
$\ S\$	Apparent Power	Volt-Ampere
$\ v\$	Voltage	volt
$\ V\$	Alternating Voltage	volt
$\ X\$	Reactance	ohm
$\ Y\$	Admittance	siemens
$\ Z\$	Impedance	ohm

Signals and systems

Symbol	Meaning	SI Units of Measure
$\ t\$	time	seconds
$\ j\$	the imaginary unit	dimensionless
$\ e\$	base of the natural logarithm 2.71828...	dimensionless
$\ \pi \$	ratio of the circumference to the diameter of a circle 3.1415927...	dimensionless
$\ \tau \$	time constant	seconds
$\ \alpha \$	exponential decay constant or attenuation coefficient	nepers per second (1/second)
$\ \theta \$	instantaneous angle in argument of sinusoid	radians (dimensionless)
$\ \phi \$	phase angle	radians (dimensionless)
$\ Q\$	quality factor	dimensionless
$\ \Delta f\$	Bandwidth	hertz
$\ \zeta \$	damping factor	dimensionless
$\ \rho _{xy}\$	Correlation between x and y	dimensionless
$\ \sigma _{x}\$	Standard deviation of x	same units as x
$\ {\overline {x}}\$	Mean value of x	same units as x
$\ E(X)\$	Expected value of the random variable X	same units as X
$\ \mu _{n}\$	nth moment of a function	nth power of the domain's units
$\ R_{XX}(t,t+\tau )\$	Autocorrelation of random process X(t)	watts
$\ S_{XX}(j\omega )\$	Power spectral density of random process X(t)	watts per hertz