An authoritative opinion is one that is convincing, accurate, reliable, and backed by leading experts.
An authentic object or person is actual or real; it or they are not fake.
An authoritarian system, such as a government or military school, demands that people obey all orders without question.
When one person authorizes another to do something, they are given official permission to do it.
Authority is the power to command or having control over something or someone.
establish the authenticity of something
be the author of
having been written
a document giving an official instruction or command
the act of creating written works
not endowed with authority
Differentiated vocabulary for your students is just a click away.