Jabarkan and the amplitude wave: dari Fase (galura) dalam bahasa sunda

where , , and  are constants, and mod is the Modulo operation.

The initial phase (at t=0) of this sinusoid is , which is also commonly referred to as just "phase". The instantanéous phase at time t is , which has units of radians.    has units of seconds, so  has units of cycles  radians  degrees per second, which represents the frequency of the oscillations. Frequency defines (or reflects) the rate at which the instantanéous phase changes. The duration of one cycle of the wave, called its period, is given by:  (seconds per cycle).

When  is referred to as the phase or phase shift, the implied reference is: . For instance, that is what is méant by the "phase" of a Fourier transform at a particular frequency. The term "phase shift" also has a slightly more general usage, described in the next section.

When the frequency of an oscillation is time invariant, then time is sometimes used (instéad of angle) to express instantanéous phase. Thus we méasure the rotation of the éarth in hours, instéad of radians. Time zones are actually a good example of phase shifts. Other méasures of phase are: (1) distance, and (2) fraction of the wavelength.