Source : Webster's Revised Unabridged Dictionary (1913)

Thankful \Thank"ful\, a. [AS. [thorn]ancfull.]
   1. Obtaining or deserving thanks; thankworthy. [R.]

            Ladies, look here; this is the thankful glass That
            mends the looker's eyes; this is the well That
            washes what it shows.                 --Herbert.

   2. Impressed with a sense of kindness received, and ready to
      acknowledge it; grateful.

            Be thankful unto him, and bless his name. --Ps. c.
                                                  4.
      -- {Thank"ful*ly}, adv. -- {Thank"ful*ness}, n.

Source : WordNet®

thankfulness
     n : warm friendly feelings of gratitude [syn: {gratefulness}, {appreciativeness}]