noun (n)

• a change for the better; progress in development(noun.event)

  Synonym:
  advance, improvement
  

  source: wordnet30
• an improvement that adds to the value of a property or facility(noun.state)

  source: wordnet30
• the act of relieving ills and changing for the better(noun.act)

  Synonym:
  amelioration, melioration
  

  source: wordnet30
• A making better; amendment; improvement.(noun)

  source: webster1913