Bengal tiger vs tiger

Bengal tiger and tiger both are nouns.

Word	Noun	Adjective	Verb	Adverb
Bengal tiger	Yes	No	No	No
tiger	Yes	No	No	No

As nouns, tiger is a hypernym of Bengal tiger; that is, tiger is a word with a broader meaning than Bengal tiger:

Bengal tiger: southern short-haired tiger
tiger: large feline of forests in most of Asia having a tawny coat with black stripes; endangered

Other hypernyms of Bengal tiger include Panthera tigris.

Bengal tiger (noun)	tiger (noun)
southern short-haired tiger	large feline of forests in most of Asia having a tawny coat with black stripes; endangered
	a fierce or audacious person