river vs Cocytus

river and Cocytus both are nouns.

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

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