Rubus saxatilis vs bramble bush

Rubus saxatilis and bramble bush both are nouns.

Word	Noun	Adjective	Verb	Adverb
Rubus saxatilis	Yes	No	No	No
bramble bush	Yes	No	No	No

As nouns, bramble bush is a hypernym of Rubus saxatilis; that is, bramble bush is a word with a broader meaning than Rubus saxatilis:

Rubus saxatilis: European trailing bramble with red berrylike fruits
bramble bush: any prickly shrub of the genus Rubus bearing edible aggregate fruits

Rubus saxatilis (noun)	bramble bush (noun)
European trailing bramble with red berrylike fruits	any prickly shrub of the genus Rubus bearing edible aggregate fruits