Definitions
1.nounThe bodies that have political or administrative power and control in a particular sphere
2.nounThe bodies that enforce law and order or provide a public service
3.nounThe power to enforce rules or give orders."I have the authority to penalise the staff in my department, but not the authority to sack them."
4.noun(used in singular or plural form) Persons in command; specifically, government.
5.nounA person accepted as a source of reliable information on a subject."the world's foremost authority on orangutans"
6.nounGovernment-owned agency which runs a revenue-generating activity.