noun Etymology: probably from rhod~ Date: 1951 any of various colorless proteins that in combination with retinal or a related prosthetic group form a visual pigment (as rhod~) in a reaction reversible by light
OPSIN
Meaning of OPSIN in English
Merriam Webster. Explanatory English dictionary Merriam Webster. Толковый словарь английского языка Мерриам-Уэбстер. 2012