Tigris vs Tigris River

Tigris and Tigris River both are nouns.

Word	Noun	Adjective	Verb	Adverb
Tigris	Yes	No	No	No
Tigris River	Yes	No	No	No

As nouns, Tigris and Tigris River are synonyms defined as:

Tigris and Tigris River: an Asian river; a tributary of the Euphrates River

Tigris (noun)	Tigris River (noun)
an Asian river; a tributary of the Euphrates River	an Asian river; a tributary of the Euphrates River