a measure of the extent to which a solution transmits radiation. It is equal to the ratio of the transmittance of the solution to the transmittance of a pure solvent of the same dimensions
transmittancy in American English
(trænsˈmɪtənsi; trænzˈmɪtənsi)
noun
1.
the ratio of the transmittance of a solution to that of an equivalent thickness of the pure solvent