Source : Webster's Revised Unabridged Dictionary (1913)

Otherness \Oth"er*ness\, n.
   The quality or state of being other or different; alterity;
   oppositeness.

Source : WordNet®

otherness
     n : the quality of being not alike; being distinct or different
         from that otherwise experienced or known [syn: {distinctness},
          {separateness}]