the characteristic pattern of dark lines or bands that occurs when electromagnetic radiation is passed through an absorbing medium into a spectroscope. An equivalent pattern occurs as coloured lines or bands in the emission spectrum of that medium
absorption spectrum in American English
a spectrum with a pattern of dark bands or lines created when light passes through a gas or liquid into a spectroscope: the chemical elements of the gas or liquid absorb specific wavelengths of light creating a unique pattern which can be used to analyze the gas or liquid chemically