Source : Webster's Revised Unabridged Dictionary (1913)

Interrelation \In`ter*re*la"tion\, n.
   Mutual or reciprocal relation; correlation.

Source : WordNet®

interrelation
     n : mutual or reciprocal relation or relatedness;
         "interrelationships of animal structure and function"
         [syn: {interrelationship}, {interrelatedness}]