ruefulness

from WordNet (r) 3.0 (2006)

ruefulness
    n 1: sadness associated with some wrong done or some
         disappointment; "he drank to drown his sorrows"; "he wrote
         a note expressing his regret"; "to his rue, the error cost
         him the game" [syn: {sorrow}, {regret}, {rue},
         {ruefulness}]

from The Collaborative International Dictionary of English v.0.48

Rueful \Rue"ful\ (r[udd]"f[.u]l), a.
   1. Causing one to rue or lament; woeful; mournful; sorrowful.
      [1913 Webster]

   2. Expressing sorrow. "Rueful faces." --Dryden.
      [1913 Webster]

            Two rueful figures, with long black cloaks. --Sir W.
                                                  Scott.
      [1913 Webster] -- {Rue"ful*ly}, adv. -- {Rue"ful*ness}, n.
      [1913 Webster]