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1. energy, in the form of heat, light, radio waves, etc., emitted from a source
2. a measure of the number of electrons emitted by a cathode or electron gun
3. Physiol any bodily discharge, esp an involuntary release of semen during sleep
1. The release of light or other radiation from an excited atom or molecule, or the radiation so emitted. See emission spectrum; nonthermal emission; thermal emission.
2. The liberation of electrons from the surface of a solid or liquid. See photoelectric effect.
Any radiation of energy by means of electromagnetic waves, as from a radio transmitter.
A natural or anthropogenic discharge of particulate, gaseous, or soluble waste material or pollution into the air.
The radiation of energy (for example, electromagnetic, heat, light, or sound).