bramble vs bramble bush

bramble and bramble bush both are nouns.

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

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

bramble: any of various rough thorny shrubs or vines
bramble bush: any prickly shrub of the genus Rubus bearing edible aggregate fruits

bramble (noun)	bramble bush (noun)
any of various rough thorny shrubs or vines	any prickly shrub of the genus Rubus bearing edible aggregate fruits