ephemeral vs impermanent

ephemeral is a noun but impermanent is not a noun.

Word	Noun	Adjective	Verb	Adverb
ephemeral	Yes	Yes	No	No
impermanent	No	Yes	No	No

ephemeral (noun)	impermanent (noun)
anything short-lived, as an insect that lives only for a day in its winged form

ephemeral (adjective)	impermanent (adjective)
lasting a very short time	not permanent; not lasting
	existing or enduring for a limited time only