A Time period (denoted by 'T' ) is the time needed for one complete cycle of vibration to pass a given point. As the frequency of a wave increases, the time period of the wave decreases. The unit for time period is 'seconds'. Frequency and time Period are in a reciprocal relationship that can be expressed mathematically as: T = 1/f or as: f = 1/T.
The period of a pendulum is the time it takes from one side to the other and back.
An electron moving in a helical orbit that has an axis at right angles to the magnetic field has a period given by T=2πm/qB, where m is the mass of the electron, q is the charge of the electron and B is the magnetic field in the region.