vapidness vs vapidity

vapidness and vapidity both are nouns.

Word	Noun	Adjective	Verb	Adverb
vapidness	Yes	No	No	No
vapidity	Yes	No	No	No

As nouns, vapidness and vapidity are synonyms defined as:

Other synonyms of vapidness include jejuneness, jejunity, tameness.

vapidness (noun)	vapidity (noun)
the quality of being vapid and unsophisticated	the quality of being vapid and unsophisticated