Greek Letters

Greek letters in maths and science

Scientists borrowed the Greek alphabet because the Latin letters were already busy. Some uses have become so standard that the letter is the name of the thing:

• π is the ratio of a circle’s circumference to its diameter, 3.14159…
• Δ (capital delta) means “change in”, as in Δt, and δ a small change or a variation.
• Σ is a sum and σ a standard deviation in statistics.
• λ is a wavelength, θ an angle, ω an angular frequency and μ the prefix micro (one millionth).
• Ω is the ohm, the unit of electrical resistance, and α, β and γ name types of radiation.

Lowercase sigma has two shapes. σ is used inside a word and ς at the end, so the word for “word” is λόγος. In maths, always use σ.

Greek or Latin? Watch the look-alikes

Capital Α, Β, Ε, Ζ, Η, Ι, Κ, Μ, Ν, Ο, Ρ, Τ, Υ and Χ look exactly like Latin letters but are different characters. If you paste Greek Α into an English word, spell-checkers, search and sorting all treat it as foreign. The same trap exists for units: the micro sign µ and the ohm sign have their own code points, although Unicode now recommends the Greek letters μ and Ω.

How to type Greek letters

For a few letters, Windows has alt codes from code page 437: Alt + 224 α, 226 Γ, 227 π, 228 Σ, 229 σ, 231 τ, 233 Θ, 234 Ω, 235 δ and 238 ε. On a Mac, Option + P gives π and Option + Z gives Ω.

If you write a lot of Greek, add the Greek keyboard layout in your system settings. On Windows go to Settings → Time & language → Language & region; on a Mac, System Settings → Keyboard → Input Sources. You can then switch layouts with Win + Space or Control + Space.

In Word’s equation editor (Alt + =), type \alpha, \beta or \Delta followed by a space. In HTML, every letter has a named entity such as α, Δ and ω. The math symbols collection has the operators that go with them.