The period defines how long a function repeats itself. Frequency instead tells us how many times a function repeats itself.

Definition

If a function has a fundamental period , then its reciprocal

is its fundamental frequency.

Frequency is typically measured in units of Hertz ().

Notations

Frequency is usually denoted as . However, in certain contexts, such as Fourier transform, it is denoted as (xi) to avoid ambiguity with the notation of functions.