Definitions:

1. an authoritative written work noun
   • this book is the final authority on the life of Milton
2. an expert whose views are taken as definitive noun
   • I am an authority on corporate law.
3. official permission or approval noun
   • authority for the program was renewed several times
4. the power or right to give orders or make decisions noun
   • The judge has the authority to issue warrants.

Synonyms:

• agency
• authorization
• sureness