- The angle between the Sun, another body and the Earth. The larger the phase angle the more of the surface of the body is illuminated from the point of view of an earthly observer.
- For two periodic quantities with the same frequency, the difference between their respective phases. Expressed in radians or degrees. For example, the phase difference between an AC and the voltage producing it. Also known as phase difference (1), or angular phase difference.
- synonymphase difference