achillea vs yarrow

achillea and yarrow both are nouns.

Word	Noun	Adjective	Verb	Adverb
achillea	Yes	No	No	No
yarrow	Yes	No	No	No

As nouns, yarrow is a hyponym of achillea; that is, yarrow is a word with a more specific, narrower meaning than achillea:

achillea: any of several plants of the genus Achillea native to Europe and having small white flowers in flat-topped flower heads
yarrow: ubiquitous strong-scented mat-forming Eurasian herb of wasteland, hedgerow or pasture having narrow serrate leaves and small usually white florets; widely naturalized in North America

Other hyponyms of achillea include Achillea millefolium, milfoil, Achillea ptarmica, sneezeweed yarrow, sneezewort.

achillea (noun)	yarrow (noun)
any of several plants of the genus Achillea native to Europe and having small white flowers in flat-topped flower heads	ubiquitous strong-scented mat-forming Eurasian herb of wasteland, hedgerow or pasture having narrow serrate leaves and small usually white florets; widely naturalized in North America