The capital Δ that means ‘change in’ across math, physics, and engineering, and the lowercase δ used for infinitesimals and the partial charges of a polar bond. Click any symbol to copy it instantly.
Delta is the fourth letter of the Greek alphabet, and its capital form, Δ (U+0394, GREEK CAPITAL LETTER DELTA), is mathematical shorthand the whole world agrees on: it means ‘change in.’ Write Δx and every scientist reads ‘the change in x’; Δt is elapsed time, ΔV a change in voltage. The lowercase form, δ (U+03B4), takes the smaller jobs — an infinitesimal change in calculus, and in chemistry the partial charges δ+ and δ− that mark the slightly positive and slightly negative ends of a polar bond. The letter's triangular capital even named a landform: the fan-shaped mouth of a river is called a ‘delta’ because its shape echoes Δ, a comparison the ancient Greeks drew for the Nile. Delta reaches into finance too, where an option's ‘delta’ measures how much the option's price moves for every $1 move in the underlying asset. One letter, a dozen fields — all built on the single idea of difference.
The Greek letter itself, in both cases. Capital Δ is the ‘change in’ sign; lowercase δ handles the smaller-scale jobs.
There is a separate math character, ∆ INCREMENT, that renders almost identically to capital delta but is a different codepoint — the same kind of look-alike trap as the ohm sign and omega. Some fonts and screen readers treat the two differently.
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The ‘change in’ delta alongside the operators, relations, and Greek letters that fill out an equation.
One of the two Greek letters the omega page displays without a link — now it has its own page. Omega closes the alphabet; delta pairs with it in math.
Another workhorse Greek letter — the summation sign in math, and the ‘sigma male’ meme online.