Definitions

For cyclical processes, such as rotation, oscillations, or waves, frequency is defined as a number of cycles per unit time. In physics and engineering disciplines, such as optics, acoustics, and radio, frequency is usually denoted by a Latin letter f or by the Greek letter ${\displaystyle \mathrm{\nu <!--\; \nu \; -->}}$ or ν (nu) (see e.g. Planck's formula).

The relation between the frequency and the period, ${\displaystyle T}$, of a repeating event or oscillation is given by

${\displaystyle f=\frac{1}{T}.}$