Source : Webster's Revised Unabridged Dictionary (1913)

Gratitude \Grat"i*tude\, n. [F. gratitude, LL. gratitudo, from
   gratus agreeable, grateful. See {Grate}, a.]
   The state of being grateful; warm and friendly feeling toward
   a benefactor; kindness awakened by a favor received;
   thankfulness.

         The debt immense of endless gratitude.   --Milton.

Source : WordNet®

gratitude
     n : a feeling of thankfulness and appreciation; "he was
         overwhelmed with gratitude for their help" [ant: {ingratitude}]