fugaciousness vs transiency

fugaciousness and transiency both are nouns.

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

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

fugaciousness: the lack of enduring qualities (used chiefly of plant parts)
transiency: an impermanence that suggests the inevitability of ending or dying

Other hypernyms of fugaciousness include transience, transitoriness.

fugaciousness (noun)	transiency (noun)
the lack of enduring qualities (used chiefly of plant parts)	an impermanence that suggests the inevitability of ending or dying