Nonlinear distortion refers to the alteration of a signal's shape in a nonlinear manner during transmission or amplification. Synonyms for this term include harmonic distortion, intermodulation distortion, and nonlinearity. Harmonic distortion arises when a circuit or system produces harmonics of the signal's fundamental frequency, while intermodulation distortion results from the mixing of different input frequencies. Nonlinearity can occur in both analog and digital systems when the relationship between input and output signals is not linear. The effects of these types of distortion can include unwanted noise, loss of clarity, and reduced dynamic range. Understanding these concepts is important in fields such as audio engineering, telecommunications, and signal processing.