In physics, there are a large number of physical quantities we include while performing calculations. To make it more convenient for users and easier to use and remember, we often use notations/symbols to represent these physical quantities. These notations/symbols we use to represent physical quantities when solving problems related to them or for other purposes are symbols.
In physics, we symbolise everything with an English/Greek alphabet, such as for the speed of light, wavelength, velocity, and so on.
Let us assume that a lady drives her car at a speed of 30 kmph and reaches her hometown in 2 hrs and if she drives at 50 kmph, she reaches in 1.5 hr. So, if we have to represent these units as symbols, how can we do that?
In this article, you will find the most popular physics symbols and also those we commonly use in physics with their names, the type of quantities along with their respective units in tabular format.
Examples of Physical Symbols
Also, the symbols used for physical quantities are vastly different. Sometimes, the symbol may be the first letter of the physical quantities they represent, like ‘d’, which stands for distance. Other times, they may be completely unrelated to the name of the physical quantities, such as c symbolises the speed of light. They may also be in the form of Greek characters, like λ, which stands for wavelength.
Below is an elaborated list of the most commonly used list of symbols in physics with their SI units. Please note that a particular symbol might relate to more than one quantity.
Symbols for Physical Quantities Related to Space and Time
Symbols | Quantity/ Coefficients | S.I. Unit | Physical Quantity (Scalar/Vector) |
r | Radius, the radius of curvature | Metre | Functions as both scalar and vector |
s | Displacement | Metre | Vector |
d | Distance | Metre | Scalar |
θ | Angular displacement, | Radian | Vector |
φ | The rotational angle | Radian | A uniquely-defined magnitude and direction, but is not a vector quantity. (Does Not obey commutative law) |
x, y, z | Cartesian Coordinates | Unitless | Scalar |
î, ĵ, k̂ | Cartesian unit vectors | Unitless | Vector |
r, θ, φ | Spherical coordinates | Metre/Radian | Vector |
r̂, θ̂, φ̂ | Spherical vectors | Unitless | Vector |
r, θ, z | Cylindrical coordinates | Metre/Radian | Scalar |
r̂, θ̂, ẑ | Cylindrical vectors | Unitless | Vector |
n̂ | Normal vector | Unitless | Vector |
t̂ | Tangential unit vector | Unitless | Vector |
h | Height, Depth | Metre | Scalar |
ℓ, L | Length | Metre | Scalar |
t | Time | Second | Scalar |
D (= 2 r) | Diameter | Metre | Scalar |
C | Circumference | Metre | Scalar |
A | Area | Square Metre | Functions as both scalar and vector (like Area vector in a magnetic flux formula) |
V | Volume | Cubic Metre (m3) | Scalar |
τ | Time Constant | Second (s) | Scalar |
T | Periodic time | Second (s) | Scalar |
f | Frequency | 1/second or (1/s) | Scalar |
ω | Angular frequency | Rad/s | Scalar |
Below are some symbols that are used frequently in physics with their names, the type of quantities and their respective SI units in tabular format.
Physics Symbols Related to Mechanics
Symbols | Quantity/ Coefficients | S.I. Unit | Physical Quantity (Scalar/Vector) |
v | Velocity, speed | metre/second (m/s) | Speed = Scalar Velocity = vector |
a | Acceleration | metre/square second (m/s2) | Vector |
g | Acceleration due to gravity | metre/square second | Vector |
ac | Centripetal/Centrifugal acceleration | metre/square second | Vector |
m | Mass | Kilogram (kg) | Scalar |
F | Force | Newton (N) | Vector |
W/Fg | Force due to gravity/Weight | Newton | Vector |
Fg/ N | Normal force | N | Vector |
Ff | Force of friction | N | Vector |
µ | Coefficient of friction | Unitless | Scalar |
p | Momentum | Kg.m/s | Vector |
J | Impulse | N/s | Vector |
E | Energy | Joule (J) | Scalar |
K | Kinetic energy | J | Scalar |
U | Potential Energy | J | Scalar |
Vg | Gravitational potential | J/kg | Scalar |
η | Efficiency | Unitless | Scalar |
P | Power | Watt | Scalar |
α | Rotational acceleration | Radian per second squared (Rad/s2) | Vector |
ω | Rotational velocity | Rad/s | Vector |
τ | Torque | N/m | Vector |
L | Angular momentum | Kilogram meter squared per second
Kg.m2/s | Vector |
ρ | Density Volume Mass density | Kilogram per cubic meter | Scalar |
I | Moment of inertia | Kg.m2 | Scalar |
Physical Symbols Related to Fluid Mechanics
Symbols | Quantity/ Coefficients | S.I. Unit | Physical Quantity (Scalar/Vector) |
λ | Linear mass density | kg/m | Scalar |
σ | Area mass density | Kilogram per square meter (kg/m2) | Scalar |
FB, B | Buoyancy | N | Vector |
qm | Mass flow rate | kg/s | Scalar |
qV | Volume flow rate | m3/s | Scalar |
FD, R | Drag or air resistance | N | Vector |
CD | Drag Coefficient | Unitless | Scalar |
η | Viscosity | Pascal-second | Scalar |
v | Kinematic Viscosity | m2/s | Scalar |
σ | Area mass density | kg/m2 | Scalar |
Re | Reynolds number | Unitless | Scalar |
Fr | Froude number | Unitless | Scalar |
Ma | Mach number | Unitless | Scalar |
Symbols Related to Solid Mechanics
Symbols | Quantity/ Coefficients | S.I. Unit | Physical Quantity (Scalar/Vector) |
P | Pressure | Pascal Or N/m2 | Scalar |
σ | Stress | Pascal | Scalar |
τ | Shear stress | Pascal | Scalar |
k | Spring constant | N/m | Scalar |
E | Young’s modulus of elasticity | Pascal | Scalar |
G | Shear modulus of rigidity | Pascal | Scalar |
ε | Linear strain | Unitless | Scalar |
γ | Shear strain | Unitless | Scalar |
θ | Volume strain | Unitless | Scalar |
S | Surface Tension | N/m | Scalar |
K | Bulk modulus of compression | Pascal | Scalar |
Physical Quantities Related to Thermal Physics
Symbols | Quantity/ Coefficients | S.I. Unit | Physical Quantity (Scalar/Vector) |
k | Thermal conductivity | W/m.K | Scalar |
P | Heat flow rate | Watt | Scalar |
N | Number of particles | Unitless | Scalar |
n | Amount of substance | Mole | Scalar |
L | Latent heat/specific latent heat | J/kg | Scalar |
c | Specific heat capacity | J/kg. K | Scalar |
Q | Heat | J | Scalar |
B | Volume expansivity, coefficient of volume thermal expansion | 1/K (inverse Kelvin) | Scalar |
α | Linear expansivity, coefficient of thermal expansion | 1/K (inverse Kelvin) | Scalar |
T | Temperature | Kelvin | Scalar |
Physical Symbol Related to Wave and Optics
Symbol | Quantity/Coefficients | S.I Unit | Physical Quantity (Scalar/Vector) |
M | Magnification | Untiless | Scalar |
f | Focal length | Metre | Scalar |
n | Index of refraction | Unitless | Scalar |
L | Level | Decibel (dB), decineper | Scalar |
I | Intensity | W/m2 | Scalar |
v, c | Wave speed | m/s | Scalar |
λ | Wavelength | Metre (m) | Scalar |
P | Power of a lens | Dioptre (D) | Scalar |
Physics Symbols Related to Electricity and Magnetism
Symbol | Quantity/Coefficients | S.I Unit | Physical Quantity (Scalar/Vector) |
S | Poynting vector, intensity | W/m2 | Vector |
η | Energy density | J/m3 | Scalar |
n | Turns per unit length | 1/m | Scalar |
N | Number of turns | Unitless | Scalar |
φB | Magnetic flux | Weber | Vector |
B | Magnetic field | Tesla | Vector |
FB | Magnetic force | N | Vector |
σ | Conductivity | Siemens/m (S/m) | Scalar |
G | Conductance | Siemens | Scalar |
ρ | Resistivity | Ohm-m | Scalar |
R, r | Electric resistance/internal resistance | Ohm | Scalar |
I | Electric current | Ampere (A) | Scalar |
ϵ | Dielectric constant | Unitless | Scalar |
ℰ | Electromotive Force | Volt (V) | Scalar |
C | Capacitance | Farad (F) | Scalar |
V | Voltage, electric potential | V | Scalar |
UE | Electric potential energy | J | Scalar |
φE | Electric flux | Newton meter squared per coulomb (N/m2.C) | Vector |
E | Electric field | N/C or V/m | Vector |
FE | Electrostatic force | N | Vector |
λ | Linear charge density | kg/m | Scalar |
σ | Area charge density | kg/m2 | Scalar |
ρ | Volume charge density | kg/m3 | Scalar |
q, Q | Electric charge | Coulomb (C) | Scalar |
Symbols Used in Modern Physics
Symbol | Quantity/Coefficients | S.I Unit | Physical Quantity (Scalar/Vector) |
D | Dose/ dose absorbed | Gray (Gy) | Scalar |
t1⁄2 | Half-life | Second | Vector |
ψ(r,t), ψ(r)φ(t) | Wave function | Unitless | Scalar |
W | Work function | J | Scalar |
H | Effective Dose | Sievert | Scalar |
Γ | Lorentz factor/Lorentz gamma | Unitless | Scalar |
From the above text on physics symbols, we understand that in Physics, we use various symbols or notations to denote different quantities. The denotations make the representation of the quantities easier.
It was also interesting to see that some physics symbols were very relatable (like “d” for distance) while some were unrelatable (like “c” for the speed of light or “λ” for wavelength). Also, we noticed that a particular symbol was related to more than one quantity.
