Delta Symbol

The capital Greek letter Delta (Δ) commonly denotes a finite change or difference of a quantity, such as Δx for the change in x. In geometry it labels a triangle, in algebra it represents the discriminant of a polynomial, and in analysis it names the Laplace operator. In chemistry, Δ written above a reaction arrow indicates that heat is applied.

The Greek small letter delta δ is the fourth letter of the Greek alphabet. In calculus it denotes a small positive quantity, famously paired with epsilon in limit definitions, and it also appears as the Kronecker delta δ_ij, which equals 1 when i = j and 0 otherwise. In physics and engineering the Dirac delta δ(x) models an idealized impulse, and in finance δ measures an option's sensitivity to the underlying price.