western saxifrage vs breakstone

western saxifrage and breakstone both are nouns.

Word	Noun	Adjective	Verb	Adverb
western saxifrage	Yes	No	No	No
breakstone	Yes	No	No	No

As nouns, breakstone is a hypernym of western saxifrage; that is, breakstone is a word with a broader meaning than western saxifrage:

western saxifrage: saxifrage having loose clusters of white flowers on hairy stems growing from a cluster of basal leaves; moist slopes of western North America
breakstone: any of various plants of the genus Saxifraga

Other hypernyms of western saxifrage include rockfoil, saxifrage.

western saxifrage (noun)	breakstone (noun)
saxifrage having loose clusters of white flowers on hairy stems growing from a cluster of basal leaves; moist slopes of western North America	any of various plants of the genus Saxifraga