ephemeralness vs transiency

ephemeralness and transiency both are nouns.

Word	Noun	Adjective	Verb	Adverb
ephemeralness	Yes	No	No	No
transiency	Yes	No	No	No

As nouns, transiency is a hypernym of ephemeralness; that is, transiency is a word with a broader meaning than ephemeralness:

ephemeralness: the property of lasting for a very short time
transiency: an impermanence that suggests the inevitability of ending or dying

Other hypernyms of ephemeralness include transience, transitoriness.

ephemeralness (noun)	transiency (noun)
the property of lasting for a very short time	an impermanence that suggests the inevitability of ending or dying