holly vs gallberry

holly and gallberry both are nouns.

Word	Noun	Adjective	Verb	Adverb
holly	Yes	No	No	No
gallberry	Yes	No	No	No

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

holly: any tree or shrub of the genus Ilex having red berries and shiny evergreen leaves with prickly edges
gallberry: evergreen holly of eastern North America with oblong leathery leaves and small black berries

holly (noun)	gallberry (noun)
any tree or shrub of the genus Ilex having red berries and shiny evergreen leaves with prickly edges	evergreen holly of eastern North America with oblong leathery leaves and small black berries