The Collaborative International Dictionary of English v.0.48:

Joyful \Joy"ful\, a.
   Full of joy; having or causing joy; very glad; as, a joyful
   heart. "Joyful tidings." --Shak.
   [1913 Webster]

         My soul shall be joyful in my God.       --Is. lxi. 10.
   [1913 Webster]

         Sad for their loss, but joyful of our life. --Pope.
   -- Joy"ful*ly, adv. -- Joy"ful*ness, n.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

joyfulness \joyfulness\ n.
   the emotion of great happiness.

   Syn: joy, joyousness.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

joyfulness
    n 1: the emotion of great happiness [syn: joy, joyousness,
         joyfulness] [ant: sorrow]

Moby Thesaurus II by Grady Ward, 1.0:

56 Moby Thesaurus words for "joyfulness":
   amusement, beatification, beatitude, bewitchment, blessedness,
   bliss, blissfulness, cheer, cheerfulness, cloud nine, delectation,
   delight, ecstasy, ecstatics, elation, enchantment, exaltation,
   exhilaration, exuberance, felicity, frivolity, fun, gaiety,
   gladness, glee, gleefulness, happiness, heaven, high glee,
   high spirits, hilariousness, hilarity, intoxication, jocularity,
   jocundity, jolliness, jollity, joviality, joy, joyance, joyousness,
   laughter, levity, merriment, merriness, mirth, mirthfulness,
   overhappiness, overjoyfulness, paradise, rapture, ravishment,
   seventh heaven, sunshine, transport, unalloyed happiness