melioration

1. 1. The act or process of improving something or the state of being improved.
   2. An improvement.
2. The linguistic process by which a word over a period of time grows more elevated in meaning or more positive in connotation.

noun

1. The act of making better or the condition of being made better: amelioration, amendment, betterment, improvement, upgrade. See better/worse.
2. Steady improvement, as of an individual or a society: amelioration, betterment, development, improvement, progress. See better/worse.

The noun has 3 meanings:

Meaning #1: the act of relieving ills and changing for the better
  Synonyms: amelioration, betterment

Meaning #2: a condition superior to an earlier condition
  Synonym: improvement

Meaning #3: the linguistic process in which over a period of time a word grows more positive in connotation or more elevated in meaning