prolongation vs fermata

prolongation and fermata both are nouns.

Word	Noun	Adjective	Verb	Adverb
prolongation	Yes	No	No	No
fermata	Yes	No	No	No

As nouns, fermata is a hyponym of prolongation; that is, fermata is a word with a more specific, narrower meaning than prolongation:

prolongation: the consequence of being lengthened in duration
fermata: (music) a prolongation of unspecified length on a note or chord or rest

prolongation (noun)	fermata (noun)
the act of prolonging something	(music) a prolongation of unspecified length on a note or chord or rest
amount or degree or range to which something extends	a musical notation (over a note or chord or rest) that indicates it is to be prolonged by an unspecified amount
the consequence of being lengthened in duration