Source : Webster's Revised Unabridged Dictionary (1913)

Changeableness \Change"a*ble*ness\, n.
   The quality of being changeable; fickleness; inconstancy;
   mutability.

Source : WordNet®

changeableness
     n : the quality of being changeable; having a marked tendency to
         change; "the changeableness of the weather" [syn: {changeability}]
         [ant: {changelessness}]