From the conductive, resistive, and hybrid forms of the phenomenological equations for electrokinetic streaming and electroosmosis phenomena in the linear domain, a generalization to the nonlinear range is proposed. The relationships that link the nonlinear phenomenological coefficients of the different forms are obtained through a set of generalized coefficients. The possibility of utilizing two phenomenological equations, each corresponding to a different form, to describe an electrokinetic effect requires that they be equivalent. This permits their correct expression to be determined as a power series of the nonzero independent variable. The experimental results shown in the final part of this study seem to confirm the validity of our treatment.