Engraving and EngravingsRheiformes: An order of large, long-necked, long-legged, flightless birds, found in South America. Known as rheas, they are sometimes called American ostriches, though they are in a separate order from true OSTRICHES.Lasers: An optical source that emits photons in a coherent beam. Light Amplification by Stimulated Emission of Radiation (LASER) is brought about using devices that transform light of varying frequencies into a single intense, nearly nondivergent beam of monochromatic radiation. Lasers operate in the infrared, visible, ultraviolet, or X-ray regions of the spectrum.Gold Alloys: Alloys that contain a high percentage of gold. They are used in restorative or prosthetic dentistry.