silk tree vs albizzia

silk tree and albizzia both are nouns.

Word	Noun	Adjective	Verb	Adverb
silk tree	Yes	No	No	No
albizzia	Yes	No	No	No

As nouns, albizzia is a hypernym of silk tree; that is, albizzia is a word with a broader meaning than silk tree:

silk tree: attractive domed or flat-topped Asiatic tree having bipinnate leaves and flowers with long silky stamens
albizzia: any of numerous trees of the genus Albizia

Other hypernyms of silk tree include albizia.

silk tree (noun)	albizzia (noun)
attractive domed or flat-topped Asiatic tree having bipinnate leaves and flowers with long silky stamens	any of numerous trees of the genus Albizia