optic density

ab·sor·bance (A, A),

(ab-sōr'bants),

spectrophotometry log of the ratio of the radiant power of the incident radiation to the radiant power of the transmitted radiation.

Synonym(s): absorbancy, absorbency, extinction (2) , optic density

ab·sor·bance

(ăb-sōr'băns)

spectrophotometry 2 minus the log of the percentage transmittance of light.
Synonym(s): extinction (2) , optic density.