An authoritative opinion is one that is convincing, accurate, reliable, and backed by leading experts.
An authentic object or person is actual or real as opposed to fake or not the real thing.
An authoritarian system, such as a government or military school, demands obedience from its subjects and allows them no individual say.
When someone authorizes someone to do something, they give that person official permission to do it.
Authority is the power to command or control over something or someone.
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