rōˈdäpsə̇n noun
( -s )
Etymology: International Scientific Vocabulary rhod- + ops- (from Greek opsis sight) + -in — more at -opsis
: a brilliant red photosensitive pigment in the retinal rods of marine fishes and most higher vertebrates that is important in vision in dim light and that is quickly bleached by light to a mixture of opsin and the retinene related to vitamin A 1 and is regenerated in the dark — called also visual purple ; compare optogram , porphyropsin