The term disperser (or dispersing element) refers
to the part of a spectrometer that disperses incoming light by
wavelength, i.e., directs the light differently
according to its wavelength so that the spectrum is evident.
Bending the light's direction according to wavelength to spread it out
in such manner is termed dispersion, or more specifically,
chromatic dispersion.
Example dispersers are prisms, gratings, grisms, and Fabry-Pérot cavities.