rhodopsin vs photopigment

rhodopsin and photopigment both are nouns.

Word	Noun	Adjective	Verb	Adverb
rhodopsin	Yes	No	No	No
photopigment	Yes	No	No	No

As nouns, photopigment is a hypernym of rhodopsin; that is, photopigment is a word with a broader meaning than rhodopsin:

rhodopsin: a red photopigment in the retinal rods of vertebrates; dissociates into retinene by light
photopigment: a special pigment found in the rods and cones of the retina

rhodopsin (noun)	photopigment (noun)
a red photopigment in the retinal rods of vertebrates; dissociates into retinene by light	a special pigment found in the rods and cones of the retina