Second-order harmonics represent an alternating current waveform or audio signal component that oscillates at exactly twice the frequency of the fundamental wave. For example, in a 60 Hertz electrical system, the second harmonic occurs at 120 Hertz. As an even-order harmonic, it typically points toward asymmetrical waveform distortion, half-wave rectification issues, or DC offset imbalances in electronic circuits. While even-order harmonics are relatively rare in balanced three-phase industrial utility grids, they frequently appear in single-phase power supplies, audio amplifier clipping stages, and unbalanced circuits, contributing to overall distortion profiles.