Source : Webster's Revised Unabridged Dictionary (1913)

Helpful \Help"ful\, a.
   Furnishing help; giving aid; assistant; useful; salutary.

         Heavens make our presence and our practices Pleasant
         and helpful to him!                      --Shak.
   -- {Help"ful*ly}, adv. -- {Help"ful*ness}, n. --Milton.

Source : WordNet®

helpfulness
     n 1: the property of providing useful assistance
     2: friendliness evidence by a kindly and helpful disposition
        [syn: {kindliness}]