pho·to·chro·mic I. \¦fōd.ə¦krōmik\adjective (-s) Etymology:phot- + chrom- + -ic 1.: capable of changing color on exposure to radiant energy (as light) < photochromic glass > < photochromic lenses > 2.: of, relating to, or utilizing the change of color shown by a photochromic substance < a photochromic process > • pho·to·chro·mism\-ˌmizəm \noun II. \"\noun (-s) : a photochromic substance — usually used in plural