stupid vs stupidity

stupid and stupidity both are nouns.

Word	Noun	Adjective	Verb	Adverb
stupid	Yes	Yes	No	No
stupidity	Yes	No	No	No

stupid (noun)	stupidity (noun)
a person who is not very bright	a stupid mistake
	a poor ability to understand or to profit from experience

stupid (adjective)	stupidity (adjective)
lacking or marked by lack of intellectual acuity
lacking intelligence
in a state of mental numbness especially as resulting from shock