In this work, a nonlinearity measure is used to examine the relative severity of various classes of inherently nonlinear behavior. Using the Optimal Control Structure, the analysis inlcudes a study of how the classes and their properties affect systems’ control-relevant nonlinearity. Two chemical reactor systems that demonstrate a wide range of nonlinear behaviors are examined. The results indicate that the nonlinearity measure is able to distinguish between the different categories of nonlinear behavior. The control-relevant anlysis indicates that the open-loop behavior may or may not necessarily transfer to the control-relevant setting.