Quadrature

The component of the complex signal that is 90 degrees out of phase with the inphase component. This component lies along the imaginary axis the complex plane.

The state of being separated in phase by 90° (/2 radians). 2. Pertaining to the phase relationship between two periodic quantities varying with the same period, that is, with the same frequency or repetition rate, when the phase difference between them is one-quarter of their period.