Nonlinear distortion occurs when a signal is altered in a way that does not maintain a direct proportionality between input and output. This can happen in various systems, such as audio equipment or electronic circuits, where the output signal may become distorted, leading to unwanted changes in sound or data quality. In audio systems, for example, nonlinear distortion can create harmonics that were not present in the original sound, affecting the clarity and fidelity of the audio. Understanding and managing nonlinear distortion is crucial for engineers working with audio technology and signal processing to ensure high-quality performance.