Reduction reactions induced by light. Common processes are: 1, addition of one or more electrons to a photoexcited species; 2, the photochemical hydrogenation of a substance. Reactions in which the substrate is not electronically excited are sometimes called photoinitiated reductions.
See also: photooxidation
PAC, 1996, 68, 2223. 'Glossary of terms used in photochemistry (IUPAC Recommendations 1996)' on page 2264 (https://doi.org/10.1351/pac199668122223)