Cycle per second

The cycle per second was a once-common English name for the unit of frequency now known as the hertz. The plural form was typically used, often written "cycles per second", "cycles/second", "c.p.s", "c/s", "~" or just "cycles". The term comes from the fact that sound waves have a frequency measurable in their number of vibrations, or cycles, per second.

With the organization of the International System of Units in 1960, the cycle per second was officially replaced by the hertz, or reciprocal second. Symbolically, "cycle per second" units are "cycle/second", while hertz is "1/second" or . This particular mandate has been so widely adopted as to render the old 'cycle per second' all but extinct.

For higher frequencies, kilocycles (kc), as an abbreviation of kilocycles per second were often used on components or devices. Other higher units like megacycle (Mc) and less commonly kilomegacycle (kMc) were used before 1960 and in some later documents. These have modern equivalents such as kilohertz (kHz) and megahertz (MHz).