unpredictability vs inconstancy

unpredictability and inconstancy both are nouns.

Word	Noun	Adjective	Verb	Adverb
unpredictability	Yes	No	No	No
inconstancy	Yes	No	No	No

As nouns, inconstancy is a hypernym of unpredictability; that is, inconstancy is a word with a broader meaning than unpredictability:

unpredictability: the quality of being guided by sudden unpredictable impulses
inconstancy: the quality of being changeable and variable

Other hypernyms of unpredictability include changefulness.

unpredictability (noun)	inconstancy (noun)
lacking predictability	the quality of being changeable and variable
the trait of being unpredictably irresolute	unfaithfulness by virtue of being unreliable or treacherous
the quality of being guided by sudden unpredictable impulses