melioration

from WordNet (r) 3.0 (2006)

melioration
    n 1: the act of relieving ills and changing for the better [syn:
         {amelioration}, {melioration}, {betterment}]
    2: a condition superior to an earlier condition; "the new school
       represents a great improvement" [syn: {improvement},
       {melioration}] [ant: {declination}, {decline}]
    3: the linguistic process in which over a period of time a word
       grows more positive in connotation or more elevated in
       meaning

from The Collaborative International Dictionary of English v.0.48

Melioration \Mel`io*ra"tion\, n. [L. melioratio.]
   The act or operation of meliorating, or the state of being
   meliorated; improvement. --Bacon.
   [1913 Webster]