Definition of "photochemical" [pho•to•chem•ic•al]

• Of, relating to, or produced by photochemistry or by photochemical reactions (adjective)

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• "Indicative of the importance of different chemicals interacting to cause smog, is the term photochemical smog."
• "Because this type of smog forms when chemical reactions take place in the presence of sunlight, it is termed photochemical smog."
• "Puralytics, winner of this year's CleanTech Open, uses photochemical processes work to break down or remove contaminants from water."