a device that allows one to select a certain wavelength of monochromatic light from a polychromatic light source such as a xenon or mercury lamp

a devise that uses a diffraction grating or prism to disperse light into a spectrum of its constituent wavelengths

an instrument which accepts a light source as its input and can select not quite a single wavelength, but a narrow band of wavelengths

a spectrometer capable of measuring a single wavelength which can be scanned

An optical device which transmits radiation in a narrow energy band only. Commonly employs crystal, grating or multilayer optics.

A device or insturment that with an appropriate energy source may be used to provide a continous calibrated series of electromagnetic energy bands of determinable wavelength or frequency range.

a wavelength selection device used in AA spectrometers to isolate the absorbable radiation from the light source from other extraneous radiation, both from the source (non or weakly absorbing lines) and the atomizer (flame or furnace emission).

A monochromator is an optical device that transmits a mechanically selectable narrow band of wavelengths of light or other radiation chosen from a wider range of wavelengths available at the input. The name is from the Greek roots mono-, single, and chroma, colour, and the Latin suffix -ator, denoting an agent.