Absorptance

Part of speech: noun

Pronunciation: /əbˈzɔːp.tn̩s/

Definitions

1. The ratio of the amount of incident energy absorbed by a material to the total incident energy is defined as a specific property of that material
2. A specific characteristic that indicates how much energy is absorbed by a material compared to the total energy incident upon it is known
3. This term refers to the measurement of energy absorbed by a surface or medium in relation to the total energy that strikes it

Etymology: "Absorptance" is a technical coinage from physics and engineering, not an old word with a long journey. It was built in English in roughly the 20th century by attaching the suffix "-ance" to "absorption", which is itself a noun from Latin "absorptio", from "absorbere", meaning "to suck up" or "swallow". The Latin verb combines "ab-" (away, off) with "sorbere" (to suck in), so the original picture is of something drawn down and taken in. The suffix does the specialised work. "-ance" turns a verb-based noun into an abstract quantity, so "absorptance" names the measurable degree or fraction to which a surface or material absorbs incoming energy, such as light or heat. Scientists needed a precise term distinct from the general process of absorption, and the suffix gave them one.