What is another word for absorption indicator?
Pronunciation: [ɐbsˈɔːpʃən ˈɪndɪkˌe͡ɪtə] (IPA) 
Absorption indicator refers to a substance, usually a dye, that changes color when it is absorbed by a particular material or medium. In scientific and technical circles, an absorption indicator may be referred to as a colorimetric or spectrophotometric indicator, since it is often used to measure the absorption of light by a particular substance. Other synonymous terms for absorption indicator might include absorbance dye, indicator dye, or color-changing agent. These terms all refer to a substance that provides a visible indication of the presence or concentration of a particular substance based on its ability to absorb light.
