noun (n)

• a reciprocality of sentiments(noun.linkdef)

  Example:
  The mutuality of their affection was obvious.
  

  Synonym:
  mutualness
  

  source: wordnet30
• a reciprocal relation between interdependent entities (objects or individuals or groups)(noun.linkdef)

  Synonym:
  interdependence, interdependency
  

  source: wordnet30
• The quality of correlation; reciprocation; interchange; interaction; interdependence.(noun)

  source: webster1913