- the spectrum formed by electromagnetic radiation that has passed through a medium in which radiation of certain frequencies is absorbed.
- 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
- The electromagnetic spectrum, broken by a specific pattern of dark lines or bands, observed when radiation traverses a particular absorbing medium.
- The range of frequencies of electromagnetic radiation readily absorbed by a substance by virtue of its chemical composition. See more at atomic spectrum.