Multiple integral
In mathematics (specifically multivariable calculus), a multiple integral is a definite integral of a function of several real variables, for instance, f(x, y) or f(x, y, z). Integrals of a function of two variables over a region in R 2 {\displaystyle \mathbb {R} ^{2}} (the real-number plane) are called double integrals, and integrals of a function of three variables over a region in R 3 {\displaystyle \mathbb {R} ^{3}} (real-number 3D space) are called triple integrals.