Learner's definition of AUTHORITY
1 [noncount] : the power to give orders or make decisions : the power or right to direct or control someone or something
Only department managers have the authority [=right, power] to change the schedule.
Does he have the authority to do this? = (US) Does he have authority to do this?
This office has authority over personnel matters. [=this office has the power to make decisions about personnel matters]
You don't have authority over me. [=you don't have the power to give me orders]
The boss is not popular but his authority is unquestioned.
“Who gave him the authority to do this?” “He didn't do it on his own authority [=he didn't do it on his own]; he was acting under the authority of the company president.” [=the company president gave him the power to do it]
No one in authority objected to the plan. = No one in a position of authority objected to the plan. [=no one with official power to make important decisions objected to the plan]
a figure of authority = an authority figure [=a person who has authority over other people]
2 a : the confident quality of someone who knows a lot about something or who is respected or obeyed by other people b : a quality that makes something seem true or real
His sincerity added much more authority [=credibility] to the story.
Her southern accent lent authority to her performance.
His opinions lacked authority.
3 authorities [plural] : people who have power to make decisions and enforce rules and laws — often used with the 4 [count] : a person who is an expert on a subject — usually + on 5 [count] : a government organization that has control of a specified activity or area
have it on good/excellent authority
◊ If you have it on good/excellent authority that something is true, you have been told that it is true by someone you trust and believe.