river vs Irtish

river and Irtish both are nouns.

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

river (noun)	Irtish (noun)
a large natural stream of water (larger than a creek)	an Asian river that rises in the Altai Mountains in northern China and flows generally northwest to become a tributary of the Ob River