subtlety in WordNet English dictionary

1. the quality of being difficult to detect or analyze
   "you had to admire the subtlety of the distinctions he drew"
   subtlety  niceness 
   
2. a subtle difference in meaning or opinion or attitude
   "without understanding the finer nuances you can't enjoy the humor"; "don't argue about shades of meaning"
   nuance  nicety  shade  subtlety  refinement