A signal is composed of a fundamental frequency of 2 kHz and another of 4 kHz. What name is given to the 4 kHz signal?

A harmonic is a signal whose frequency is an exact integer (whole number) multiple of a base or fundamental frequency. In this scenario, the 4 kHz signal is exactly twice the fundamental frequency of 2 kHz, making it the second harmonic. Distractors like "Sub-harmonic" are incorrect because they refer to frequencies lower than the fundamental (such as 1 kHz). "Intermodulation" refers to unwanted sum and difference frequencies created when mixing multiple signals, and an "Alias" is a digital sampling artifact, not a natural frequency multiple.