A device that uses the principle of amplification of electromagnetic waves by stimulated emission of radiation, and operates in the infrared, visible, or ultraviolet region. The term laser is an acronym for light amplification by stimulated emission of radiation, or a light amplifier. However, just as an electronic amplifier can be made into an oscillator by feeding appropriately phased output back into the input, so the laser light amplifier can be made into a laser oscillator, which is really a light source. Laser oscillators are so much more common than laser amplifiers that the unmodified word “laser” has come to mean the oscillator, while the modifier “amplifier” is generally used when the oscillator is not intended.