Total Harmonic Distortion (THD) measures the distortion in a signal caused by harmonics, which are multiples of a fundamental frequency. It is expressed as a percentage, indicating how much of the signal's power is made up of these unwanted frequencies. Lower THD values suggest a cleaner, more accurate reproduction of the original signal, making it an important factor in audio equipment and electronic devices. In audio systems, high THD can lead to a loss of sound quality, affecting clarity and detail. Engineers often strive to minimize THD in devices like amplifiers and speakers to ensure a more faithful representation of the original audio.