Yenisei vs Yenisey

Yenisei and Yenisey both are nouns.

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

As nouns, Yenisei and Yenisey are synonyms defined as:

Yenisei 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 include Yenisei River, Yenisey River.

Yenisei (noun)	Yenisey (noun)
the Uralic language spoken by the Yeniseian	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