Absorption Coefficient -

: Materials often absorb certain colors better than others. For example, a blue filter has a high for red light but a low for blue light.

In acoustics, the absorption coefficient refers to the ratio of sound energy absorbed by a surface to the total sound energy incident upon it. Sound Absorption Coefficient - an overview - ScienceDirect absorption coefficient

The is a fundamental physical parameter that quantifies how effectively a medium absorbs energy—typically in the form of light or sound—as it passes through. Represented by the Greek letter : Materials often absorb certain colors better than others