Photoactive

Part of speech: adjective

Definitions

1. Having the ability to undergo transformation or reaction when interacting with light sources
2. Referring to materials that can be energized or altered by light exposure to trigger various reactions
3. Capable of reacting or changing due to exposure to light energy

Etymology: Photoactive is a plain compound: "photo-", from the Greek "phōs" (light, with the combining form "phōto-"), joined to "active". The "active" half has a longer road behind it. It descends from Latin "āctīvus", built on "āgere" (to do, drive), and came into English through Old French "actif" and Middle English "actyf". Its ancestry runs back through Latin "-īvus" and Greek "energētikos" (working, effective), which is why "active" carries the sense of doing something rather than merely existing. Put the two halves together and the word means, literally, "active toward light." Chemists and physicists use it for substances or materials that change when illuminated, such as the molecules in photographic emulsions or in some solar cells, where light supplies the energy that triggers the change. The compound follows the same pattern as older words like "photosynthesis" and "photochemical," where the Greek "phōto-" marks the light involved.