Source : Webster's Revised Unabridged Dictionary (1913)

Decorative \Dec"o*ra*tive\, a. [Cf. F. d['e]coratif.]
   Suited to decorate or embellish; adorning. --
   {Dec"o*ra*tive*ness}, n.

   {Decorative art}, fine art which has for its end
      ornamentation, rather than the representation of objects
      or events.

Source : WordNet®

decorativeness
     n : an appearance that serves to decorate and make something
         more attractive