The Collaborative International Dictionary of English v.0.48:
Variableness \Va"ri*a*ble*ness\, n. The quality or state of being variable; variability. --James i. 17. [1913 Webster]WordNet (r) 3.0 (2006):
variableness n 1: the quality of being subject to variation [syn: variability, variableness, variance] [ant: invariability, invariableness, invariance]