a quantity that has magnitude and direction

a two-dimensional mathematical quantity that rotates with a constant angular frequency and represents oscillating voltage, or current, in an AC circuit ( see figure 21.13)

A representation of a sine wave in terms of both magnitude and phase angle.

A phasor is a vector drawn to represent a wave, such that the vector sum of several phasors can be used to determine the intensity and phase of the several waves after interference. Phasors are used directly in optics, radio engineering and acoustics. The constant length of the phasor gives the amplitude and the angle it makes with the x-axis gives the phase angle.

A phasor is a constant complex number representing the complex amplitude (magnitude and phase) of a sinusoidal function of time. (In older texts, a phasor is alternatively referred to as a sinor.) It is usually expressed in exponential form.