Source : Webster's Revised Unabridged Dictionary (1913)

Distinctiveness \Dis*tinc"tive*ness\, n.
   State of being distinctive.

Source : WordNet®

distinctiveness
     n 1: a distinguishing trait [syn: {peculiarity}, {specialness}, {specialty},
           {speciality}]
     2: utter dissimilarity [syn: {disparateness}]