Irtysh River vs Irtish River

Irtysh River and Irtish River both are nouns.

Word	Noun	Adjective	Verb	Adverb
Irtysh River	Yes	No	No	No
Irtish River	Yes	No	No	No

As nouns, Irtysh River and Irtish River are synonyms defined as:

Irtysh River and Irtish River: an Asian river that rises in the Altai Mountains in northern China and flows generally northwest to become a tributary of the Ob River

Other synonyms of Irtysh River include Irtish, Irtysh.

Irtysh River (noun)	Irtish River (noun)
an Asian river that rises in the Altai Mountains in northern China and flows generally northwest to become a tributary of the Ob River	an Asian river that rises in the Altai Mountains in northern China and flows generally northwest to become a tributary of the Ob River