' may refer to:
- A negative difference between retail price and cost of production
- An event in which the team or individual in question did not win.
- Loss (baseball), a pitching statistic in baseball
- Attenuation, a reduction in amplitude and intensity of a signal
- In telecommunications, loss is a decrease in signal in a communications system:
- Angular misalignment loss, power loss caused by the deviation from optimum angular alignment
- 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.
In the arts: