variability vs changeability

variability and changeability both are nouns.

Word	Noun	Adjective	Verb	Adverb
variability	Yes	No	No	No
changeability	Yes	No	No	No

As nouns, changeability is a hypernym of variability; that is, changeability is a word with a broader meaning than variability:

variability: the quality of being subject to variation
changeability: the quality of being changeable; having a marked tendency to change

Other hypernyms of variability include changeableness.

variability (noun)	changeability (noun)
the quality of being subject to variation	the quality of being changeable; having a marked tendency to change
the quality of being uneven and lacking uniformity