rapidity vs quickness

rapidity and quickness both are nouns.

Word	Noun	Adjective	Verb	Adverb
rapidity	Yes	No	No	No
quickness	Yes	No	No	No

As nouns, rapidity and quickness are synonyms defined as:

Other synonyms of rapidity include celerity, rapidness, speediness.

rapidity (noun)	quickness (noun)
a rate that is rapid	a rate that is rapid
	intelligence as revealed by an ability to give correct responses without delay
	skillful performance or ability without difficulty