Definition of "opsin" [opsin]

• A protein of the retina, especially the protein constituent of rhodopsin, that makes up one of the visual pigments. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "The gene, called opsin, is present in vision among vertebrate animals, and is responsible for a different way of seeing than that of animals like flies."
• "I had a feeling that my Irish in-laws have a long wavelength opsin and special photoreceptors to allow them to see how hot their tea is."
• "We vertebrates have ciliary cells, c-opsin, and a phosphodiesterase pathway."