The hertz (Hz) is the SI base unit of frequency, defined as one cycle per second, measuring how often a repeating event occurs. From AC power grid frequency (50 or 60 Hz) to audio tones and processor clock speeds, hertz is the universal language of frequency. One hertz equals exactly one cycle per second.

Revolutions per second (rps) measures rotational speed as complete turns per second, equivalent to exactly one hertz. While less common than rpm in everyday specifications, rps is used in physics, engineering analysis, and some industrial equipment ratings. One rps equals exactly 60 rpm.