stability vs inconstant

stability is a noun but inconstant is not a noun.

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

stability (noun)	inconstant (noun)
the quality or attribute of being firm and steadfast
the quality of being enduring and free from change or variation
a stable order (especially of society)

stability (adjective)	inconstant (adjective)
	likely to change frequently often without apparent or cogent reason; variable