movement of an organism in response to the intensity of light, especially away from the source of light.
any condition or disease produced by the effect of light, especially in excessive amounts.

Origin of photopathy

First recorded in 1895–1900; photo- + -pathy
Related formspho·to·path·ic [foh-tuh-path-ik] /ˌfoʊ təˈpæθ ɪk/, adjective Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019