noun (n)

• approval to do something(noun.communication)

  Example:
  He asked permission to leave.
  

  source: wordnet30
• the act of giving a formal (usually written) authorization(noun.act)

  Synonym:
  license, permit
  

  source: wordnet30
• The act of permitting or allowing; formal consent; authorization; leave; license or liberty granted.(noun)

  source: webster1913