briony vs white bryony

briony and white bryony both are nouns.

Word	Noun	Adjective	Verb	Adverb
briony	Yes	No	No	No
white bryony	Yes	No	No	No

As nouns, white bryony is a hyponym of briony; that is, white bryony is a word with a more specific, narrower meaning than briony:

briony: a vine of the genus Bryonia having large leaves and small flowers and yielding acrid juice with emetic and purgative properties
white bryony: white-flowered vine having thick roots and bearing small black berries; Europe to Iran

Other hyponyms of briony include Bryonia alba, devil's turnip, Bryonia dioica, red bryony, wild hop.

briony (noun)	white bryony (noun)
a vine of the genus Bryonia having large leaves and small flowers and yielding acrid juice with emetic and purgative properties	white-flowered vine having thick roots and bearing small black berries; Europe to Iran