Physics formulas are written in symbols: F for force, m for mass, λ for wavelength, μ for the coefficient of friction. The tables below list the symbols used in introductory physics with their meaning, SI unit, and a formula where you will meet each one. Some letters mean different things in different topics, so always check the context.
A handful of letters do double duty. The units usually tell you which quantity is meant.
Symbol
Possible meanings
T
Period of an oscillation, or tension in a rope.
P
Power in watts, or pressure in pascals (often lower-case p).
p
Momentum, or pressure.
W
Weight (a force, in N), work (energy, in J), or the unit watt.
V
Voltage in volts, or volume in m³.
f
Frequency in Hz, friction force in N, or a lens’s focal length.
R
Resistance in ohms, the range of a projectile, or a radius.
Ft
Tension force Fₜ, or force × time, which is impulse (N·s).
Subscripts and Greek letters
A subscript zero, as in v₀ or x₀, marks the starting value. Δ (delta) means “change in”, so Δx is final position minus initial position. Σ (sigma) means “sum of”, so ΣF is the net force. Greek letters often name angles (θ), densities (ρ), friction coefficients (μ), wavelengths (λ), and angular frequencies (ω).
