inconstant vs volatile

inconstant is not a noun while volatile is a noun.

Word	Noun	Adjective	Verb	Adverb
inconstant	No	Yes	No	No
volatile	Yes	Yes	No	No

inconstant (noun)	volatile (noun)
	a volatile substance; a substance that changes readily from solid or liquid to a vapor

inconstant (adjective)	volatile (adjective)
likely to change frequently often without apparent or cogent reason; variable	evaporating readily at normal temperatures and pressures
	tending to vary often or widely
	marked by erratic changeableness in affections or attachments
	liable to lead to sudden change or violence