improvement
     n 1: the act of improving something; "their improvements
          increased the value of the property"
     2: a change for the better; progress in development [syn: {betterment},
         {advance}]
     3: a condition superior to an earlier condition; "the new
        school represents a great improvement" [syn: {melioration}]
        [ant: {decline}]
Source: WordNet® 2.0