A wave's period measures how long it takes for a wave to pass a given point in its entirety, from crest to crest. Frequency and period are basically measuring the same characteristic of a wave and can be related by the equation period = 1 / frequency.
Frequency is measured in hertz (Hz) which is equal to one event per second. The period is the duration of time of one cycle in a repeating event, so the period is the reciprocal of the frequency.
