noun (n)

• a feeling of sympathetic understanding(noun.feeling)

  source: wordnet30
• capability of existing or performing in harmonious or congenial combination(noun.attribute)

  Antonym:
  incompatibility
  

  source: wordnet30
• The quality or power of being compatible or congruous; congruity; as, a compatibility of tempers; a compatibility of properties.(noun)

  source: webster1913