laxity vs lax

laxity is a noun but lax is not a noun.

Word	Noun	Adjective	Verb	Adverb
laxity	Yes	No	No	No
lax	No	Yes	No	No

laxity (noun)	lax (noun)
the quality of being lax and neglectful
the condition of being physiologically lax

laxity (adjective)	lax (adjective)
	lacking in firmness or tension; not taut
	pronounced with muscles of the tongue and jaw relatively relaxed (e.g., the vowel sound in `bet')
	lacking in rigor or strictness
	emptying easily or excessively