DefinitionDouble and triple integrals are extensions of the idea of the integral to functions of two or three variables, respectively. They compute the signed volume under a topological surface or within a volume in n-dimensional space. Triple integrals are a generalization to integrate over regions (volumes, such as the cube inside the sphere) in 3-dimensional space (which are smooth 3-surfaces), while double integrals find the surface area of the well-defined regions. In areas of calculus, physics, engineering, and probability theory, double and triple integrals are methods used to determine the solutions to problems that relate to area, volume, mass, probability density, and multidimensional probability distributions. For instance, the double integral ∬Rf(x,y)dA means that it calculates the volume under the surface defined by the function f(x,y) when mapping over the region R in the xy-plane.