Emission

Emission may refer to:
 * Flue gas, also:
 * Exhaust gas, flue gas occurring as a result of the combustion of a fuel
 * Emission of air pollutants
 * Emission of greenhouse gases, a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range
 * Emission (electromagnetic radiation), the process by which the energy of a photon is released by another entity
 * Emission (radiocommunications), the radio signal (usually modulated) emitted from a radio transmitter
 * Emission coefficient, a coefficient in the power output per unit time of an electromagnetic source
 * Emission factor
 * Emission line, or "spectral line", a dark or bright line in an otherwise uniform and continuous spectrum
 * Emission nebula, a cloud of ionized gas emitting light of various colors
 * Emission spectroscopy, photoemission spectroscopy, flame emission spectroscopy and other types of spectroscopy
 * Emission standard, requirements that set specific limits to the amount of pollutants that can be released into the environment
 * Emission theory, a competing theory for the special theory of relativity, explaining the results of the Michelson-Morley experiment
 * Emission theory (vision), the proposal that visual perception is accomplished by rays of light emitted by the eyes
 * Emissions trading, a market-based approach used to control pollution by providing economic incentives for achieving reductions in the emissions of pollutants
 * Ejaculation, the ejecting of semen from the penis; also, specifically:
 * Nocturnal emission, ejaculation experienced during sleep
 * Light emission
 * Thermionic emission, the flow of charged particles called thermions from a charged metal or a charged metal oxide surface, archaically known as the Edison effect
 * Noise emission; see Noise
 * Exhalation, especially where the velocity of exhaled air can influence the harmonic generating properties of a vibrating body, such as the reed of a musical instrument like the saxophone