The integration of a function of two inputs with respect to both of those inputs. If f is a function of x and y, and R is a two-dimensional region defined by a range of values for x and y, then the double integral of f over region R is written as
A double integral is not the same in general as two single integrals, although for many well-behaved functions they give the same result. The notion can be generalized to functions with more than two inputs, such as the triple integral for functions of the form f(x,y,z).