foolishness vs imbecility

foolishness and imbecility both are nouns.

Word	Noun	Adjective	Verb	Adverb
foolishness	Yes	No	No	No
imbecility	Yes	No	No	No

As nouns, foolishness and imbecility are synonyms defined as:

Other synonyms of foolishness include betise, folly, stupidity.

foolishness (noun)	imbecility (noun)
a stupid mistake	a stupid mistake
the trait of acting stupidly or rashly	retardation more severe than a moron but not as severe as an idiot
the quality of being rash and foolish