noun
plural -ties
[noncount] :the power to give orders or make decisions :the power or right to direct or control someone or something
synonyms see1power</SYNR
[noncount] the confident quality of someone who knows a lot about something or who is respected or obeyed by other people
a quality that makes something seem true or real
authorities [plural] :people who have power to make decisions and enforce rules and laws
[count] :a person who is an expert on a subject - usually + on
[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.