Source : Webster's Revised Unabridged Dictionary (1913)

Sum \Sum\, v. t. [imp. & p. p. {Summed}; p. pr. & vb. n.
   {Summing}.] [Cf. F. sommer, LL. summare.]
   1. To bring together into one whole; to collect into one
      amount; to cast up, as a column of figures; to ascertain
      the totality of; -- usually with up.

            The mind doth value every moment, and then the hour
            doth rather sum up the moments, than divide the day.
                                                  --Bacon.

   2. To bring or collect into a small compass; to comprise in a
      few words; to condense; -- usually with up.

            ``Go to the ant, thou sluggard,'' in few words sums
            up the moral of this fable.           --L'Estrange.

            He sums their virtues in himself alone. --Dryden.

   3. (Falconry) To have (the feathers) full grown; to furnish
      with complete, or full-grown, plumage.

            But feathered soon and fledge They summed their pens
            [wings].                              --Milton.

   {Summing up}, a compendium or abridgment; a recapitulation; a
      r['e]sum['e]; a summary.

   Syn: To cast up; collect; comprise; condense; comprehend;
        compute.

Source : WordNet®

sum
     n 1: a quantity of money; "he borrowed a large sum"; "the amount
          he had in cash was insufficient" [syn: {sum of money}, {amount},
           {amount of money}]
     2: a quantity obtained by addition [syn: {amount}, {total}]
     3: the final aggregate; "the sum of all our troubles did not
        equal the misery they suffered" [syn: {summation}, {sum
        total}]
     4: the choicest or most essential or most vital part of some
        idea or experience; "the gist of the prosecutor's
        argument"; "the heart and soul of the Republican Party";
        "the nub of the story" [syn: {kernel}, {substance}, {core},
         {center}, {essence}, {gist}, {heart}, {heart and soul}, {inwardness},
         {marrow}, {meat}, {nub}, {pith}, {nitty-gritty}]
     5: the whole amount [syn: {total}, {totality}, {aggregate}]
     6: the basic unit of money in Uzbekistan
     7: a set containing all and only the members of two or more
        given sets; "let C be the union of the sets A and B" [syn:
         {union}, {join}]
     [also: {summing}, {summed}]

sum
     v 1: be a summary of; "The abstract summarizes the main ideas in
          the paper" [syn: {summarize}, {summarise}, {sum up}]
     2: determine the sum of; "Add all the people in this town to
        those of the neighboring town" [syn: {total}, {tot}, {tot
        up}, {sum up}, {summate}, {tote up}, {add}, {add together},
         {tally}, {add up}]
     [also: {summing}, {summed}]

summing
     See {sum}