river vs Neckar River

river and Neckar River both are nouns.

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

river (noun)	Neckar River (noun)
a large natural stream of water (larger than a creek)	a river in Germany; rises in the Black Forest and flows north into the Rhine