eucalyptus vs white ash

eucalyptus and white ash both are nouns.

Word	Noun	Adjective	Verb	Adverb
eucalyptus	Yes	No	No	No
white ash	Yes	No	No	No

As nouns, white ash is a hyponym of eucalyptus; that is, white ash is a word with a more specific, narrower meaning than eucalyptus:

eucalyptus: a tree of the genus Eucalyptus
white ash: small to medium-sized tree of Australia and Tasmania having smooth white to light-grey bark shedding in patches or strips

eucalyptus (noun)	white ash (noun)
a tree of the genus Eucalyptus	spreading American ash with leaves pale green or silvery beneath and having hard brownish wood
wood of any of various eucalyptus trees valued as timber	small to medium-sized tree of Australia and Tasmania having smooth white to light-grey bark shedding in patches or strips