Yenisei River vs Yenisey River

Yenisei River and Yenisey River both are nouns.

Word	Noun	Adjective	Verb	Adverb
Yenisei River	Yes	No	No	No
Yenisey River	Yes	No	No	No

As nouns, Yenisei River and Yenisey River are synonyms defined as:

Yenisei River and Yenisey River: a Russian river in Siberia; rises in mountains near the Mongolian border and flows generally northward into the Kara Sea

Other synonyms of Yenisei River include Yenisei, Yenisey.

Yenisei River (noun)	Yenisey River (noun)
a Russian river in Siberia; rises in mountains near the Mongolian border and flows generally northward into the Kara Sea	a Russian river in Siberia; rises in mountains near the Mongolian border and flows generally northward into the Kara Sea