noun (n)

• the process of declining from a higher to a lower level of effective power or vitality or essential quality(noun.process)

  Synonym:
  devolution
  Antonym:
  development, evolution
  

  source: wordnet30
• the state of being degenerate in mental or moral qualities(noun.state)

  Synonym:
  decadence, decadency, degeneracy
  

  source: wordnet30
• passing from a more complex to a simpler biological form(noun.event)

  Synonym:
  retrogression
  

  source: wordnet30
• The act or state of growing worse, or the state of having become worse; decline; degradation; debasement; degeneracy; deterioration.(noun)

  source: webster1913