river vs Nile River

river and Nile River both are nouns.

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

river (noun)	Nile River (noun)
a large natural stream of water (larger than a creek)	the world's longest river (4150 miles); flows northward through eastern Africa into the Mediterranean; the Nile River valley in Egypt was the site of the world's first great civilization