cps

cycle per second

Frequencyexact by definition

The cycle per second is exactly one hertz. It is the older name for the same unit, universal in engineering literature and on equipment nameplates before the hertz was adopted, and it is still spoken in some trades.

1 cps 1 Hz
Where the unit came from

The CGPM adopted the hertz in 1960, honouring Heinrich Hertz for demonstrating electromagnetic waves. Older American equipment is marked "60 cycles" or "60 c/s" and means exactly what a modern nameplate marked 60 Hz means.