noun (n)

• the act of leaving secretly or without explanation(noun.act)

  Synonym:
  disappearing
  Antonym:
  appearance
  

  source: wordnet30
• the event of passing out of sight(noun.event)

  source: wordnet30
• gradually ceasing to be visible(noun.act)

  Synonym:
  fade
  

  source: wordnet30
• ceasing to exist(noun.event)

  Example:
  He regretted the disappearance of Greek from school curricula.
  What was responsible for the disappearance of the rainforest?.
  The disappearance of resistance at very low temperatures.
  

  source: wordnet30
• The act of disappearing; cessation of appearance; removal from sight; vanishing.(noun)

  source: webster1913