phase factor

For any complex number written in polar form (such as re^iθ), the phase factor is the complex exponential factor (e^iθ). As such, the term "phase factor" is related to the more general term phasor, which may have any magnitude (i.e., not necessarily part of the circle group). The phase factor is a unit complex number, i.e., of absolute value 1. It is commonly used in quantum mechanics.