Bridging loss, the loss that results when an impedance is connected across a transmission line
Coupling loss, the loss that occurs when energy is transferred from one circuit, optical device, or medium to another
Insertion loss, the decrease in transmitted signal power resulting from the insertion of a device in a transmission line or optical fiber
Path loss, the attenuation undergone by an electromagnetic wave in transit from a transmitter to a receiver
Free-space path loss, the loss in signal strength that would result if all influences were sufficiently removed having no effect on its propagation
Reflection loss, a loss which causes energy to be reflected back toward its source
Return loss, the ratio of the amplitude of the reflected wave to the amplitude of the incident wave
in laser physics, loss (or background loss, or round-trip loss) may refer to the part of the energy of the optical field, that becomes unusable at each rond-trip in the cavity due to the scattering or absorption.