Definitions of authority:

• noun:   official permission or approval

  Example: "Authority for the program was renewed several times"

• noun:   the power or right to give orders or make decisions

  Example: "He has the authority to issue warrants"

• noun:   an authoritative written work

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

• noun:   an expert whose views are taken as definitive

  Example: "He is an authority on corporate law"

• noun:   (usually plural) persons who exercise (administrative) control over others
• noun:   freedom from doubt; belief in yourself and your abilities

  Example: "She spoke with authority"

• noun:   an administrative unit of government

  Example: "Tennessee Valley Authority"