a. [ Gr. fw^s, fwto`s, light. ] Of or pertaining to light; specifically, relating to the production of light by the lower animals. [ Webster 1913 Suppl. ]

. (Phytogeography) The uppermost zone of the sea, which receives the most light. [ Webster 1913 Suppl. ]

n. (Physics) The science of light; -- a general term sometimes employed when optics is restricted to light as a producing vision. Knight. [ 1913 Webster ]