“…4 This was possible due to cyclic identities satisfied by the Jacobi elliptic functions where the nonlinear cross terms reduce to, and combine with, other linear terms. 5 Other examples include time modes of nonlinear systems, 6 Einstein nonlinear electrodynamics (NLE) equations, 7 nonlinear gas governing equations, 8 the Novikov-Veselov equation, 9 Maxwell-Schrödinger equations, 10 the (2 + 1)-dimensional KdV equations, 11 Caudrey-Dodd-Gibbon-Sawada-Kotera (CDGSK) equation and the (2 + 1)-dimensional Nizhnik-Novikov-Veselov (NNV) equation, 12 the (2 + 1)-dimensional Sawada-Kotera (SK) equation, 13 the (3 + 1)-dimensional Jimbo-Miwa (JM) equations, 14 the (2 + 1)-dimensional Calogero-Bogoyavlenskii-Schiff (CBS) equation, 15 higher order NLSE, 16 coupled nonlinear Klein-Gordon and Schrödinger equations, 17 the (2 + 1)-dimensional modified Zakharov-Kuznetsov (ZK) equation and the (3 + 1)-dimensional KP equation, 18 the (2 + 1)-dimensional ZK equation and the Davey-Stewartson (DS) equation, 19 generalized KdV equation, the Oliver water wave equation, the k(n; n) equation, 20 the fifth-order KdV equation, 21 the cubic-quintic NLSE, 22 Hirota bilinear equations, 23,24 and the (2 + 1)-dimensional Boussinesq equation. 25 The main property that allows for the application of superposition principle to all of the above-mentioned nonlinear systems is the reduction of the nonlinear cross terms into linear ones, which then combine with other linear terms.…”