1.the power or right to give orders or make decisions;
he has the authority to issue warrants
2.(usually plural) persons who exercise (administrative) control over others;
the authorities have issued a curfew
3.an expert whose views are taken as definitive;
he is an authority on corporate law
4.freedom from doubt; belief in yourself and your abilities;
his assurance in his superiority did not make him popular
5.an administrative unit of government;
the Central Intelligence Agency
6.official permission or approval;
authority for the program was renewed several times
7.an authoritative written work;
this book is the final authority on the life of Milton