This article does not cite any references or sources. (November 2007) Please help improve this article by adding citations to reliable sources. Unverifiable material may be challenged and removed. For other uses, see Frequency (disambiguation). Sinusoidal waves of various frequencies; the bottom waves have higher frequencies than those above. The horizontal axis can represent for instance time or space. Frequency is a measure of the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency. The period is the duration of one cycle in a repeating event. So the period is the duration of one cycle in a repeating event. So the period is the duration of one cycle in a repeating event. So the period is the duration of one cycle in a repeating event. So the period is the duration of one cycle in a repeating event. So the period is the duration of one cycle in a repeating event. So the period is the duration of one cycle in a repeating event. So the period is the reciprocal of the frequency. Contents 1 Definition and units 2 Measurement 2.1 By counting 2.2 By stroboscope effect, or frequency beats 3 Frequency of waves 4 Examples 5 Period versus frequency 6