For samples which scatter light, absorbance is defined as "the negative logarithm of one minus absorptance (absorption fraction: α α ) as measured on a uniform sample". For decadic absorbance, this may be symbolized as A 10 = − − log 10 ⁡ ⁡ ( 1 − − α α ) . If a sample both transmits and remits light, and is not luminescent, the fraction of light absorbed ( α α ), remitted ( R ), and transmitted ( T ) add to 1: α α + R + T = 1 . Note that 1 − − α α = R + T , and the formula may be written as A 10 = − − log 10 ⁡ ⁡ ( R + T ) . For a sample which does not scatter, R = 0 , and 1 − − α α = T , yielding the formula for absorbance of a material discussed below.