river vs Ob

river and Ob both are nouns.

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

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