Ob River vs river

Ob River and river both are nouns.

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

Ob River (noun)	river (noun)
a major river of western Siberia; flows generally northward and westward to the Gulf of Ob and the Kara Sea	a large natural stream of water (larger than a creek)