'Niceness' definitions:

Definition of 'niceness'

From: WordNet
noun
A courteous manner that respects accepted social usage [syn: politeness, niceness] [ant: impoliteness]
noun
The quality of nice [ant: nastiness]
noun
The quality of being difficult to detect or analyze; "you had to admire the subtlety of the distinctions he drew" [syn: subtlety, niceness]

Definition of 'Niceness'

From: GCIDE
  • Niceness \Nice"ness\, n. Quality or state of being nice. [1913 Webster]