tiger vs tigress

tiger and tigress both are nouns.

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

As nouns, tigress is a hyponym of tiger; that is, tigress is a word with a more specific, narrower meaning than tiger:

tiger: large feline of forests in most of Asia having a tawny coat with black stripes; endangered
tigress: a female tiger

Other hyponyms of tiger include tiger cub, Bengal tiger.

tiger (noun)	tigress (noun)
large feline of forests in most of Asia having a tawny coat with black stripes; endangered	a female tiger
a fierce or audacious person