ephemeral vs short-lived

ephemeral is a noun but short-lived is not a noun.

Word	Noun	Adjective	Verb	Adverb
ephemeral	Yes	Yes	No	No
short-lived	No	Yes	No	No

As adjectives, ephemeral and short-lived are synonyms defined as:

Other synonyms of ephemeral include fugacious, passing, transient, transitory.

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

ephemeral (adjective)	short-lived (adjective)
lasting a very short time	lasting a very short time