American bison vs Bison bison

American bison and Bison bison both are nouns.

Word	Noun	Adjective	Verb	Adverb
American bison	Yes	No	No	No
Bison bison	Yes	No	No	No

As nouns, American bison and Bison bison are synonyms defined as:

American bison and Bison bison: large shaggy-haired brown bison of North American plains

Other synonyms of American bison include American buffalo, buffalo.

American bison (noun)	Bison bison (noun)
large shaggy-haired brown bison of North American plains	large shaggy-haired brown bison of North American plains