weak vs human

weak is not a noun while human is a noun.

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

weak (noun)	human (noun)
	any living or extinct member of the family Hominidae characterized by superior intelligence, articulate speech, and erect carriage

weak (adjective)	human (adjective)
wanting in physical strength	having human form or attributes as opposed to those of animals or divine beings
overly diluted; thin and insipid	characteristic of humanity
tending downward in price	relating to a person
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