In Physics, we use numerous symbols or notations to denote various quantities. These denotations make the representation and understanding of the quantities much easier.

In this article, we will touch upon the majority of the most popular physics symbols.

**Nature of Physics Symbols**

It’s interesting to note that a few physics symbols are pretty common and confusing (such as “d” for distance), while a few are unrelatable (such as “c” for the speed of light). Now, that may generate confusion!

Below is a well-elaborated list of the most commonly used physics symbols with their SI units. Not that a specific symbol might relate to multiple quantities as well.

**Symbols for physical quantities and their international units: **

**Space & Time**

Symbol |
Quantity |
SI unit |

s, s | displacement, distance | meter |

r, r | position, separation, radius, the radius of curvature | meter |

x, y, z | cartesian coordinates | meter |

θ, φ, θ, φ | angle, angular displacement, angular separation, rotation angle | radian |

r, θ, φ | spherical coordinates | meter, radian |

î, ĵ, k̂ | cartesian unit vectors | unitless |

ρ, φ, z | cylindrical coordinates | meter, radian |

r̂, θ̂, φ̂ | spherical unit vectors | unitless |

n̂ | normal unit vector | unitless |

ρ̂, φ̂, ẑ | cylindrical unit vectors | unitless |

h | height, depth | meter |

t̂ | tangential unit vector | unitless |

d | distance, separation, thickness | meter |

ℓ, L | length | meter |

D | diameter | meter |

t | thickness | meter |

A, A | area, cross-sectional area, projected area, surface area | square meter |

C | circumference | meter |

t | time, duration | second |

V | volume | cubic meter |

τ | time constant | second |

T | period, periodic time | second |

ω | angular frequency | radian per second |

f | frequency | hertz |

**Mechanics**

Symbol |
Quantity |
SI unit |
Symbol |

a, a | acceleration | meter per second squared | m/s2 |

v, v | velocity, speed | meter per second | m/s |

g, g | gravitational field, acceleration due to gravity | meter per second squared | m/s2 |

ac, ac | centripetal acceleration, centrifugal acceleration | meter per second squared | m/s2 |

F, F | force | newton | N |

m | mass | kilogram | kg |

Fn, N, N | normal force, normal | newton | N |

Fg, W, W | force of gravity, weight | newton | N |

μs, μk | coefficient of friction (static, kinetic) | unitless | |

Ff, fs, fk | force of friction (static, kinetic) | newton | N |

J, J | impulse | newton second | Ns |

p, p | momentum | kilogram meter per second | kg m/s |

E | energy, total energy | joule | J |

W | work | joule | J |

U, Ug, Us | potential energy (gravitational, spring) | joule | J |

K, Kt, Kr | kinetic energy (translational, rotational) | joule | J |

η | efficiency | unitless | |

Vg | gravitational potential | joule per kilogram | J/kg |

ω, ω | rotational velocity, rotational speed | radian per second | rad/s |

P | power | watt | W |

τ, τ | torque | newton meter | N m |

α, α | rotational acceleration | radian per second squared | rad/s2 |

L, L | angular momentum | kilogram meter squared per second | kg m2/s |

I | moment of inertia | kilogram meter squared | kg m2 |

k | spring constant | newton per meter | N/m |

H, H | angular impulse | newton meter second | N m s |

σ | normal stress | pascal | Pa |

P | pressure | pascal | Pa |

ρ | density, volume mass density | kilogram per cubic meter | kg/m3 |

τ | shear stress | pascal | Pa |

λ | linear mass density | kilogram per meter | kg/m |

σ | area mass density, superficial mass density | kilogram per square meter | kg/m2 |

qm | mass flow rate | kilogram per second | kg/s |

FB, B, B | buoyancy, buoyant force | newton | N |

FD, R, R | drag, aerodynamic drag, air resistance | newton | N |

qV | volume flow rate | cubic meter per second | m3/s |

η | viscosity, dynamic viscosity | pascal second | Pa s |

C, CD | drag coefficient, coefficient of drag | unitless | |

Ma | mach number | unitless | |

ν | kinematic viscosity | square meter per second | m2/s |

Fr | Froude number | unitless | |

Re | Reynolds number | unitless | |

G | shear modulus, modulus of rigidity | pascal | Pa |

E | young’s modulus, modulus of elasticity | pascal | Pa |

ε | linear strain | unitless | |

K | bulk modulus, modulus of compression | pascal | Pa |

θ | volume strain | unitless | |

γ | shear strain | unitless | |

γ | surface tension | newton per meter | N/m |

**Thermal Physics**

Symbol |
Quantity |
SI unit |
Symbol |

α | linear expansivity, coefficient of linear thermal expansion | inverse kelvin | K−1 |

T | temperature | kelvin | K |

Q | heat | joule | J |

β | volume expansivity, coefficient of volume thermal expansion | inverse kelvin | K−1 |

L | latent heat, specific latent heat | joule per kilogram | J/kg |

c | specific heat, specific heat capacity | joule per kilogram kelvin | J/kg K |

N | number of particles | unitless | |

n | amount of substance | mole | |

k | thermal conductivity | watt per meter kelvin | W/m K |

P | heat flow rate | watt | W |

U | internal energy | joule | J |

ε | emissivity | unitless | |

w | ways, number of identical microstates | unitless | |

S | entropy | joule per kelvin | J/K |

COP | coefficient of performance | unitless |

**Waves & Optics**

Symbol |
Quantity |
SI unit |
Symbol |

v, c | wave speed | meter per second | m/s |

λ | wavelength | meter | m |

L | level | decibel, decineper | dB, dNp |

I | intensity | watt per square meter | W/m2 |

f | focal length | meter | m |

n | index of refraction, absolute index of refraction | unitless | |

M | magnification | unitless |

**Electricity & Magnetism**

Symbol |
Quantity |
SI unit |
Symbol |

ρ | charge density, volume charge density | coulomb per cubic meter | C/m3 |

q, Q | charge, electric charge | coulomb | C |

λ | linear charge density | coulomb per meter | C/m |

σ | area charge density, superficial charge density | coulomb per square meter | C/m2 |

E, E | electric field | newton per coulomb, volt per meter | N/C, V/m |

FE, FE | electric force, electrostatic force | newton | N |

U, UE | potential energy, electric potential energy | joule | J |

ΦE | electric flux | newton meter squared/coulomb, volt meter | N m2/C, V m |

ℰ | electromotive force, emf | volt | V |

V, VE | voltage, potential, electric potential | volt | V |

κ | dielectric constant | unitless | |

C | capacitance | farad | F |

R, r | resistance, electrical resistance, internal resistance | ohm | Ω |

I | current, electric current | ampère | A |

G | conductance | siemens | S |

ρ | resistivity | ohm meter | Ω m |

FB, FB | magnetic force | newton | N |

σ | conductivity | Siemens per meter | S/m |

ΦB | magnetic flux | weber | Wb |

B, B | magnetic field | tesla | T |

n | turns per unit length turns density | inverse meter | m−1 |

N | number of turns | unitless | |

η | energy density | joule per cubic meter | J/m3 |

**Conclusion**

Yes, they are a lot and truly a lot. They truly never seem to end, but when you try to learn the first twenty, you’d certainly feel that these aren’t that tough. So, do one thing – go slow and steady! Practice and remember these signs and symbols since they are going to help you in numerous exams.