A surface integral is a generalization of multiple integrals to integration over surfaces. It can be thought of as the double integral analog of the line integral. To find an explicit formula for the surface integral, we need to parameterize the surface of interest, "S", by considering a system of curvilinear coordinates on "S", like the latitude and longitude on a sphere. Let such a parameterization be x("s", "t"), where ("s", "t") varies in some region "T" in the plane. Then, the surface integral is given by