Cycle per second Cycle per second The cycle per second was a once-common English name for the unit of frequency now known as the hertz (Hz). The plural form was typically used, often written cycles per second, cycles/second, c.p.s., c/s, ~, or, ambiguously, just cycles. The term comes from the fact that sound waves have a frequency measurable in their number of oscillations, 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, "s" or "1/s". Symbolically, "cycle per second" units are "cycle/second", while hertz
SI base unit referenced to the values of the fundamental constants, namely the Planck constant ("h"), the electron charge ("e"), the Boltzmann constant ("k"), and the Avogadro constant ("N"). This approach was approved in 2018, only after measurements of these constants were achieved with sufficient accuracy. SI base unit The International System of Units (SI) defines seven units of measure as a basic set from which all other SI units can be derived. The SI base units and their physical quantities are the meter for measurement of length, the kilogram for mass, the second for time, the ampere for electric current, the kelvin