mother-of-thousands vs rockfoil

mother-of-thousands and rockfoil both are nouns.

Word	Noun	Adjective	Verb	Adverb
mother-of-thousands	Yes	No	No	No
rockfoil	Yes	No	No	No

As nouns, rockfoil is a hypernym of mother-of-thousands; that is, rockfoil is a word with a broader meaning than mother-of-thousands:

mother-of-thousands: eastern Asiatic saxifrage with racemes of small red-and-white flowers; spreads by numerous creeping stolons
rockfoil: any of various plants of the genus Saxifraga

Other hypernyms of mother-of-thousands include breakstone, saxifrage.

mother-of-thousands (noun)	rockfoil (noun)
eastern Asiatic saxifrage with racemes of small red-and-white flowers; spreads by numerous creeping stolons	any of various plants of the genus Saxifraga