river vs Ruhr

river and Ruhr both are nouns.

Word	Noun	Adjective	Verb	Adverb
river	Yes	No	No	No
Ruhr	Yes	No	No	No

river (noun)	Ruhr (noun)
a large natural stream of water (larger than a creek)	a major industrial and coal mining region in the valley of the Ruhr river in northwestern Germany
	a tributary of the Rhine