river vs Rio Bravo

river and Rio Bravo both are nouns.

Word	Noun	Adjective	Verb	Adverb
river	Yes	No	No	No
Rio Bravo	Yes	No	No	No

river (noun)	Rio Bravo (noun)
a large natural stream of water (larger than a creek)	a North American river; boundary between the United States and Mexico; flows into Gulf of Mexico