Linearization of nonlinear systems about constant operating points

For bilinear-realizable nonlinear systems described by a Volterra series, an input-output definition of the linearized system about a constant operating point is given. This definition is then compared to the usual notion of linearization in terms of a bilinear realization of the nonlinear system. Properties of the linearized system with respect to the original nonlinear system are developed, and implications for analysis and design of nonlinear systems are discussed.