river vs Nan River

river and Nan River both are nouns.

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

river (noun)	Nan River (noun)
a large natural stream of water (larger than a creek)	a river of western Thailand flowing southward to join the Ping River to form the Chao Phraya