非线性系统
至少有一个重要性能参数呈非线性变化的系统——即该参数的性能曲线斜率不是常数。在非线性系统中，任一工作点上的性能不能线性外推到任何其他工作点。因此，非线性系统的分析比线性系统要困难得多。有时可以假设系统在有限范围内呈线性响应，从而简化分析。
非线性系统的例子包括屈曲、含铁芯电感电路的电振荡，以及具有非线性回复力的机械系统。压电材料的大多数性能都是非线性的。
Nonlinear system
A system in which at least one important performance parameter varies nonlinearly -- i.e., the slope of the performance curve for such a parameter is not constant. In a nonlinear system, the performance at any operating point cannot be linearly scaled to any other operating point. As such, the analysis of nonlinear systems is much more difficult than for linear systems. Analysis can sometimes be simplified by assuming that the system response is linear over a limited range.
Examples of nonlinear systems include buckling, electrical oscillations of circuits containing iron core inductors, and mechanical systems with nonlinear restoring forces. Most properties of piezoelectric materials are nonlinear.