Reflected Power in the transmission line increases the average current and therefore losses in the transmission line compared to power actually delivered to the load. It is the interaction of these reflected waves with forwarding waves that cause standing wave patterns, with negative repercussions.

Reflection Coefficient is defined as the ratio of the reflected wave to incident wave at a reference plane.  This value varies from -1 (for a shorted load) to +1 (for an open load) and becomes 0 for matched impedance load. The reflection coefficient is a parameter that describes how much of an electromagnetic wave is reflected by an impedance discontinuity in the transmission medium. The voltage reflection coefficient  Γ determines the magnitude and phase of the reflected wave given the incident wave, the characteristic impedance of the transmission line, and the terminating impedance.