fermata vs lengthiness

fermata and lengthiness both are nouns.

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

As nouns, lengthiness is a hypernym of fermata; that is, lengthiness is a word with a broader meaning than fermata:

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

Other hypernyms of fermata include continuation, prolongation, protraction.

fermata (noun)	lengthiness (noun)
(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