∆

From the Greek capital letter Δ.

∆

1. (mathematics) An increment or change in a variable.

   ∆x   a large change in variable x

2. (set theory) The symmetric difference symbol.
3. (mathematics, physics) The Laplace operator.

• Although this is the official encoding for the mathematical character, most math publications that apply unicode (LaTeX publications rarely use Unicode) use simply the Greek letter Δ for convenience.

• Δ