Encyclopedia of magnetics and electromagnetics.
Hz or hertz - a unit of frequency, reciprocal of cycle or period.
According to the SI terminology, hertz is a coherent derived unit, because it can be derived from the base unit of second by raising to the power of -1. Hertz can only be applied to period phenomena.1)
by S. Zurek, E. Magnetica, CC-BY-3.0
In older publications the phrase cycles per second (or c.p.s.) was used to denote frequency, and it was a unit synonymous with hertz so that 1 cps = 1 Hz.2)3)