volatile vs inconstant

volatile is a noun but inconstant is not a noun.

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

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

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