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### Phase

The **phase** of a periodic phenomenon at time *t* is its relative position to the period since the beginning of a new cycle.

##### Explanation

The phase of a periodic function *F* of some real variable *t* (such as time) is an angle-like quantity representing the fraction of the cycle covered up to *t*.

It is denoted *Φ* (*t*) and expressed in such a scale that it varies by one full turn as the variable *t* goes through each period (and *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 2π as the variable *t* completes a full period.