Phase is defined as the time relationship between two corresponding points on a continuous wave, or the angular, or time, displacement between the voltage and current in an AC circuit. A sine wave signal is the simplest possible waveform and goes through 360˚ in one cycle, whereby it returns to its starting point. Another way of saying the same thing is that the signal has gone through 360˚ of phase angle, or phase change. The phase is actually a measure of time, 360˚ equaling one period of the signal. The time represented by a phase change of a certain number of degrees is thus dependent on frequency.