Bison bison vs bison

Bison bison and bison both are nouns.

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

As nouns, bison is a hypernym of Bison bison; that is, bison is a word with a broader meaning than Bison bison:

Bison bison: large shaggy-haired brown bison of North American plains
bison: any of several large humped bovids having shaggy manes and large heads and short horns

Bison bison (noun)	bison (noun)
large shaggy-haired brown bison of North American plains	any of several large humped bovids having shaggy manes and large heads and short horns