silver-bush vs oleaster

silver-bush and oleaster both are nouns.

Word	Noun	Adjective	Verb	Adverb
silver-bush	Yes	No	No	No
oleaster	Yes	No	No	No

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

silver-bush: 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

silver-bush (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