botanical garden vs arboretum

botanical garden and arboretum both are nouns.

Word	Noun	Adjective	Verb	Adverb
botanical garden	Yes	No	No	No
arboretum	Yes	No	No	No

As nouns, botanical garden and arboretum are synonyms defined as:

botanical garden and arboretum: a facility where trees and shrubs are cultivated for exhibition

botanical garden (noun)	arboretum (noun)
a facility where trees and shrubs are cultivated for exhibition	a facility where trees and shrubs are cultivated for exhibition