stupidity vs stupid

stupidity and stupid both are nouns.

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

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

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