noun (n)

• a subtle difference in meaning or opinion or attitude(noun.communication)

  Synonym:
  nicety, nuance, refinement, shade
  

  source: wordnet30
• the quality of being difficult to detect or analyze(noun.attribute)

  Example:
  You had to admire the subtlety of the distinctions he drew.
  

  Synonym:
  niceness
  

  source: wordnet30
• The quality or state of being subtle, or sly; cunning; craftiness; artfulness.(noun)

  source: webster1913