noun (n)

• the power or right to give orders or make decisions(noun.attribute)

  Example:
  He has the authority to issue warrants.
  

  Synonym:
  authorisation, authorization, dominance, potency, say-so
  

  source: wordnet30
• (usually plural) persons who exercise (administrative) control over others(noun.person)

  source: wordnet30
• an expert whose views are taken as definitive(noun.person)

  Example:
  He is an authority on corporate law.
  

  source: wordnet30
• freedom from doubt; belief in yourself and your abilities(noun.cognition)

  Example:
  She spoke with authority.
  

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

  source: wordnet30
• an administrative unit of government(noun.group)

  Example:
  Tennessee Valley Authority.
  

  Synonym:
  agency, bureau, federal agency, government agency, office
  

  source: wordnet30
• official permission or approval(noun.attribute)

  Example:
  Authority for the program was renewed several times.
  

  Synonym:
  authorisation, authorization, sanction
  

  source: wordnet30
• an authoritative written work(noun.communication)

  Example:
  This book is the final authority on the life of Milton.
  

  source: wordnet30
• Legal or rightful power; a right to command or to act; power exercised buy a person in virtue of his office or trust; dominion; jurisdiction; authorization; as, the authority of a prince over subjects, and of parents over children; the authority of a court.(noun)

  source: webster1913