weak vs stupid

weak is not a noun while stupid is a noun.

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

weak (noun)	stupid (noun)
	a person who is not very bright

weak (adjective)	stupid (adjective)
wanting in physical strength	lacking or marked by lack of intellectual acuity
overly diluted; thin and insipid	lacking intelligence
tending downward in price	in a state of mental numbness especially as resulting from shock
likely to fail under stress or pressure
lacking bodily or muscular strength or vitality
wanting in moral strength, courage, or will; having the attributes of man as opposed to e.g. divine beings
deficient in magnitude; barely perceptible; lacking clarity or brightness or loudness etc
not having authority, political strength, or governing power
(used of verbs) having standard (or regular) inflection
deficient in intelligence or mental power
deficient or lacking in some skill
(used of vowels or syllables) pronounced with little or no stress