retinal purple vs rhodopsin

retinal purple and rhodopsin both are nouns.

Word	Noun	Adjective	Verb	Adverb
retinal purple	Yes	No	No	No
rhodopsin	Yes	No	No	No

As nouns, retinal purple and rhodopsin are synonyms defined as:

retinal purple and rhodopsin: a red photopigment in the retinal rods of vertebrates; dissociates into retinene by light

Other synonyms of retinal purple include visual purple.

retinal purple (noun)	rhodopsin (noun)
a red photopigment in the retinal rods of vertebrates; dissociates into retinene by light	a red photopigment in the retinal rods of vertebrates; dissociates into retinene by light