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Definition

noun

(spectrophotometry)

The measure of how strongly a substance absorbs light at a particular wavelength, and is usually represented by the unit M-1cm-1 or L mol-1cm-1.

Supplement

It is symbolized by ε in Beer-Lambert law, A = εcl, where A is the absorbance of the sample, l is the pathlength (usually in centimeter), and c is the concentration of the of absorbing species in the material (moles per liter).

Synonym: molar absorptivity, molar absorption coefficient, absorbancy index, absorptivity, molar absorbancy index.
See also: spectrophotometer, absorbance.