dichroism

Dependence of absorbance of a sample on the type of polarization of the measuring beam. This polarization may be linear, corresponding to linear dichroism (LD) in which the difference in absorption for two perpendicularly linearly polarized beams is measured, $Δ A l = A Z − A Y$ , or circular dichroism (CD) in which the difference in absorption for left minus right circularly polarized beams is measured, $Δ A C = A L − A R$ .

Source:

PAC, 2007, 79, 293 (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 324