Yenisei River vs Yenisey

Yenisei River and Yenisey both are nouns.

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

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

Yenisei River and Yenisey: 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 River.

Yenisei River (noun)	Yenisey (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