River Cocytus vs river

River Cocytus and river both are nouns.

Word	Noun	Adjective	Verb	Adverb
River Cocytus	Yes	No	No	No
river	Yes	No	No	No

River Cocytus (noun)	river (noun)
(Greek mythology) a river in Hades that was said to be a tributary of the Acheron	a large natural stream of water (larger than a creek)