[1] : WordNet (r) 2.0

absorptance
     n : a measure of the rate of decrease in the intensity of
         electromagnetic radiation as light as it passes through
         a given substance; the fraction of incident radiant
         energy absorbed per unit mass or thickness of an
         absorber; "absorptance equals 1 minus transmittance"
         syn: absorption coefficient, coefficient of
         absorption
see also:
absorption coefficient coefficient of absorption 

Absorptance >> A Words
Absorptance, definition of term: Absorptance
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