Source : Webster's Revised Unabridged Dictionary (1913)

Interdependency \In`ter*de*pend"en*cy\, n.
   Mutual dependence; as, interdependency of interests. --De
   Quincey.

Source : WordNet®

interdependency
     n : a reciprocal relation between interdependent entities
         (objects or individuals or groups) [syn: {mutuality}, {interdependence}]