noun (n)

• freedom from doubt; belief in yourself and your abilities(noun.cognition)

  Example:
  His assurance in his superiority did not make him popular.
  

  Synonym:
  authority, confidence, self-assurance, self-confidence, sureness
  

  source: wordnet30
• a binding commitment to do or give or refrain from something(noun.communication)

  Example:
  An assurance of help when needed.
  

  Synonym:
  pledge
  

  source: wordnet30
• a statement intended to inspire confidence(noun.communication)

  Example:
  The President's assurances were not respected.
  

  source: wordnet30
• a British term for some kinds of insurance(noun.possession)

  source: wordnet30
• The act of assuring; a declaration tending to inspire full confidence; that which is designed to give confidence.(noun)

  source: webster1913