Nonlinear control (control engineering) is a subfield of control theory dedicated to the analysis and design of control systems for dynamic systems whose behavior is accurately represented by nonlinear mathematical models, typically involving nonlinear differential or difference equations. Unlike linear control methods, which are applicable to systems satisfying the principle of superposition, nonlinear control addresses systems exhibiting complex phenomena such as saturation, hysteresis, dead zones, friction, multiple equilibria, limit cycles, and bifurcations. It investigates techniques for achieving objectives such as stabilization, tracking, regulation, and optimization in the presence of these nonlinearities, often employing advanced mathematical tools and methodologies like Lyapunov stability analysis, feedback linearization, sliding mode control, and adaptive control. Its significance lies in providing the necessary theoretical framework and practical methods for controlling a vast array of real-world processes and systems across diverse engineering disciplines and scientific fields that inherently display significant nonlinear characteristics.