river vs Kasai River

river and Kasai River both are nouns.

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

river (noun)	Kasai River (noun)
a large natural stream of water (larger than a creek)	a river of southwestern Africa that rises in central Angola and flows east and then north (forming part of the border between Angola and Congo) and continuing northwest through Congo to empty into the Congo River on the border between Congo and Republic of the Congo