flexibleness vs adaptability

flexibleness and adaptability both are nouns.

Word	Noun	Adjective	Verb	Adverb
flexibleness	Yes	No	No	No
adaptability	Yes	No	No	No

As nouns, adaptability is a hypernym of flexibleness; that is, adaptability is a word with a broader meaning than flexibleness:

flexibleness: the quality of being adaptable or variable
adaptability: the ability to change (or be changed) to fit changed circumstances

flexibleness (noun)	adaptability (noun)
the property of being flexible; easily bent or shaped	the ability to change (or be changed) to fit changed circumstances
the quality of being adaptable or variable