Frequency is the number of occurrences of a repeating event per unit
time. It is also referred to as
temporal frequency, which emphasizes the contrast to
spatial frequency and
angular frequency. The
period is the duration of time of one
cycle in a repeating event, so the period is the
reciprocal of the frequency. For example, if a newborn baby's heart beats at a frequency of 120 times a minute, its period – the interval between beats – is half a second (60 seconds (i.e., a minute) divided by 120
beats). Frequency is an important parameter used in science and engineering to specify the rate of
oscillatory and
vibratory phenomena, such as mechanical vibrations,
audio (
sound) signals,
radio waves, and
light.
