The absorption coefficient is a property of a material. It defines the extent to which a material absorbs energy, for example, that of sound waves or electromagnetic radiation. Wallace Sabine was a pioneer of this concept in acoustics and defined the unit of the Sabine. A Sabine is defined as a fraction of acoustic power absorbed by a 1m square of open window. In SI units, absorption coefficient is measured in inverse metersand is represented by the Greek letter.
In chemistry and biological sciences, the absorption coefficient is a measure of the solubility of a gas in a liquid measured as the volume of the gas (taken under standard conditions) that saturates a unit volume of the liquid.