# phase

**phase: 1.** Of a periodic, varying phenomenon, *e.g.,* an electrical signal or electromagnetic wave, any distinguishable instantaneous state of the phenomenon, referred to a fixed reference or another periodic varying phenomenon. (188) *Note 1:* Phase, *i.e.,* *phase time* (frequently abbreviated simply to "phase" in colloquial usage), can be specified or expressed by time of occurrence relative to a specified reference. *Note 2:* The phase of a periodic phenomenon can also be expressed or specified by angular measure, with one period usually encompassing 360° (2 radians). *Note 3:* Phase may be represented (a) in polar coordinates by *M* , where *M* is the magnitude and is the phase angle, and (b) in Cartesian coordinates, *i.e.* , an Argand diagram, as (*a* + j*b* ), where *a* is a real component and *b* is an imaginary component such that tan = (*b* /*a* ), where is the phase angle, and the magnitude, *M* , is (*a* ^{2} + *b* ^{2})^{½} **2.** A distinguishable state of a phenomenon. (188) **3.** That period of time during which a specified function occurs in a sequential list of functions. (188)

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