Delta symbol Δ

• Change: Δx = x₂ − x₁. If the temperature rises from 60 °F to 75 °F, ΔT = 15 °F. Physics writes average velocity as Δx/Δt.
• Difference, as shorthand: engineering and finance teams write “the Δ between plan and actual.”
• Discriminant: in algebra, Δ = b² − 4ac tells you how many real roots a quadratic equation has.
• Laplace operator: in advanced math and physics, Δ also denotes the Laplacian.
• River deltas: the triangular landform at a river mouth is named after the letter’s shape.

Lowercase δ usually means a small change or a small quantity, as in the epsilon-delta definition of a limit.

• ∆ (increment) is a separate math character, U+2206, that looks identical in most fonts. Both are used for “change in.” They are different characters to a computer, so a search for one won’t find the other; pick one and use it consistently.
• ▲ and △ are geometric shapes, used as bullets, warning icons and play buttons. △ABC is the usual way to name a triangle in geometry, but that is the triangle shape, not the letter delta.
• ∇ (nabla) is the upside-down triangle used for the gradient in vector calculus.

If you are writing Greek text or a Greek-letter organization name, use the Greek letter Δ from this page.

• Word: in an equation (Alt+=), type \Delta for Δ or \delta for δ and press space.
• LaTeX: \Delta and \delta; \nabla gives ∇.
• Excel: Δ is only a label. Compute the change with a formula such as =B2-A2, and the percent change with =(B2-A2)/A2.
• Phones: add the Greek keyboard, or copy Δ here and save a text replacement.
• Mac Character Viewer: Control+Command+Space, then search “delta” to see the Greek letters and the increment sign side by side.