(born) A perturbation solution of the integral equations for scattering. This involves sub-stituting the unperturbed wavefield for the unknown wavefield under the integral sign, to obtain the first approximation. The second approximation is obtained by substituting the first approximation for the unknown wavefield, and so on. Named for Max Born (1882–1970), German physicist. See Clayton and Stolt (1981) and Cohen et al. (1986).