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pho·to·chem·i·cal .fōt-ō-'kem-i-kəl adj
1) of, relating to, or resulting from the chemical action of radiant energy and esp. light <\photochemical smog>
2) of or relating to photochemistry <\photochemical studies>
pho·to·chem·i·cal·ly -k(ə-)lē adv
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pho·to·chem·i·cal (fo″to-kemґə-kəl) pertaining to the chemical properties of light; chemically reactive in the presence of light or other radiation.Medical dictionary. 2011.