Phase (waves)

Elapsed fraction of a cycle of a periodic function

In physics and mathematics, the phase (symbol φ or ϕ) of a wave or other periodic function F {\displaystyle F} of some real variable t {\displaystyle t} (such as time) is an angle-like quantity representing the fraction of the cycle covered up to t {\displaystyle t} . It is expressed in such a scale that it varies by one full turn as the variable t {\displaystyle t} goes through each period (and F ( t) {\displaystyle F(t)} goes through each complete cycle). It may be measured in any angular unit such as degrees or radians, thus increasing by 360° or 2 π {\displaystyle 2\pi } as the variable t {\displaystyle t} completes a full period.

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