immediacy vs rapidness

immediacy and rapidness both are nouns.

Word	Noun	Adjective	Verb	Adverb
immediacy	Yes	No	No	No
rapidness	Yes	No	No	No

As nouns, rapidness is a hypernym of immediacy; that is, rapidness is a word with a broader meaning than immediacy:

Other hypernyms of immediacy include celerity, quickness, rapidity, speediness.

immediacy (noun)	rapidness (noun)
the quickness of action or occurrence	a rate that is rapid
lack of an intervening or mediating agency
immediate intuitive awareness