noun (n)

• abnormal hardening or thickening of tissue(noun.state)

  source: wordnet30
• the process of becoming hard or solid by cooling or drying or crystallization(noun.process)

  Example:
  The hardening of concrete.
  

  Synonym:
  curing, set, solidification, solidifying
  

  source: wordnet30
• the act of making something harder (firmer or tighter or more compact)(noun.act)

  source: wordnet30
• Making hard or harder.(noun)

  source: webster1913