silverbush vs oleaster

silverbush and oleaster both are nouns.

Word	Noun	Adjective	Verb	Adverb
silverbush	Yes	No	No	No
oleaster	Yes	No	No	No

As nouns, oleaster is a hypernym of silverbush; that is, oleaster is a word with a broader meaning than silverbush:

silverbush: deciduous unarmed North American shrub with silvery leaves and fruits
oleaster: any of several shrubs of the genus Elaeagnus having silver-white twigs and yellow flowers followed by olivelike fruits

silverbush (noun)	oleaster (noun)
deciduous unarmed North American shrub with silvery leaves and fruits	any of several shrubs of the genus Elaeagnus having silver-white twigs and yellow flowers followed by olivelike fruits
silvery hairy European shrub with evergreen foliage and pale yellow flowers