noun (n)

• being unsettled or in doubt or dependent on chance(noun.attribute)

  Example:
  The uncertainty of the outcome.
  

  Synonym:
  precariousness, uncertainness
  Antonym:
  certainty, foregone conclusion, sure thing
  

  source: wordnet30
• the state of being unsure of something(noun.cognition)

  Synonym:
  doubt, doubtfulness, dubiety, dubiousness, incertitude
  Antonym:
  certainty
  

  source: wordnet30
• The quality or state of being uncertain.(noun)

  source: webster1913