river vs Yukon River

river and Yukon River both are nouns.

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

river (noun)	Yukon River (noun)
a large natural stream of water (larger than a creek)	a North American river that flows westward from the Yukon Territory through central Alaska to the Bering Sea