Physics Symbols: Quantities, Units and Copy Paste

Italic Symbols, Upright Units: One Rule to Remember

In printed physics, the symbol for a quantity is written in italics and the unit is written in normal upright letters. So in "m = 5 kg", the italic m is mass, while the upright m in "5 m" is the metre. The same letter can mean different things, so the style matters.

• Put a space between the number and the unit: 9.8 m/s², not 9.8m/s².
• Unit symbols never take a plural s: 5 kg, not 5 kgs.
• Units named after people start with a capital: N (Newton), A (Ampère), Hz (Hertz). The full names stay small: newton, ampere, hertz.

In handwriting you cannot write italics, so just keep the letters clear and always write the unit.

Mechanics Symbols and SI Units

NCERT books use u for initial velocity and v for final velocity, so v = u + at. The tao symbol in physics is really tau (τ), used for torque and also for time constants. See the tau symbol and rho symbol pages for more uses.

Waves, Light and Modern Physics: Frequency and Wavelength Symbols

So, frequency is denoted by which symbol? The frequency symbol can be either: both f and the Greek ν are correct. School books often use ν in the photoelectric effect (E = hν) and f for sound. The symbol of wavelength is always λ, and the two are linked by v = fλ. Read more on the lambda symbol page.

The angstrom symbol is Å, where 1 Å = 10⁻¹⁰ m. It is handy for atom sizes and X-ray wavelengths but it is not an SI unit, so modern books often use nanometres (1 nm = 10 Å). Temperature in kelvin is written 300 K with no degree symbol.

Electric Symbols: Current, Voltage, Resistance

The current symbol is I, and the ampere symbol (its unit) is A. The voltage symbol is V and its unit is also V (volt), which is why the italic rule above helps. The ohm unit is the capital Greek omega, see the ohm symbol page. Conductance is the inverse of resistance (G = 1/R), and the conductivity symbol σ stands for the inverse of resistivity (σ = 1/ρ).

Circuit diagrams use drawn electric symbols: a circle with A is an ammeter, V a voltmeter, G a galvanometer and W a wattmeter. Direct current is marked DC and alternating current AC or with a wavy line ~. The 3 phase symbol is 3φ or 3~, and a single phase supply is marked 1φ, using the Greek phi as the phase symbol.

Magnetism and Materials: Flux, Field, Stress and Strain

The strain symbol ε has no unit, because strain is a change in length divided by the original length. Notice how σ means conductivity in electricity but stress in materials. Always read the chapter heading. For more on these letters see phi, epsilon, gamma and mu; the micro symbol page explains why µ also means one millionth.

Common Unit Symbols: Metre, Ampere and Prefixes

Use the proportional symbol ∝ for relations like V ∝ I, and the delta symbol Δ for change, as in Δv. The main math symbols page has every operator you need for derivations.

How to Type Physics Symbols

• Word: type the code then press Alt+X. Examples: 03BB gives λ, 03C9 gives ω, 03A9 gives Ω, 00C5 gives Å.
• Windows Alt codes (number pad, Num Lock on): Alt+234 for Ω, Alt+0197 for Å, Alt+229 for σ. Results can differ by app.
• Mac: Option+Z gives Ω and Option+D gives ∂. For other Greek letters use Control+Command+Space.
• Google Docs: Insert > Special characters and search "lambda" or "omega". Docs equations also accept \lambda.
• Phone: Greek letters are not on standard keyboards, so copy them from the grid above.