The Collaborative International Dictionary of English v.0.48:

Gladness \Glad"ness\, n. [AS. gl[ae]dnes.]
   State or quality of being glad; pleasure; joyful
   satisfaction; cheerfulness.
   [1913 Webster]

         They . . . did eat their meat with gladness and
         singleness of heart.                     --Acts ii. 46.
   [1913 Webster]

   Note: Gladness is rarely or never equivalent to mirth,
         merriment, gayety, and triumph, and it usually
         expresses less than delight. It sometimes expresses
         great joy.
         [1913 Webster]

               The Jews had joy and gladness, a feast and a good
               day.                               --Esther viii.
                                                  17.
         [1913 Webster]

WordNet (r) 3.0 (2006):

gladness
    n 1: experiencing joy and pleasure [syn: gladness,
         gladfulness, gladsomeness]