showing that you are confident, in control, and expect to be respected and obeyed

She has an authoritative manner that at times is almost arrogant. 她爱发号施令，有时几乎到了盛气凌人的地步。

containing complete and accurate information, and therefore respected

The book is an authoritative account of the Second World War. 这本书对第二次世界大战作了非常权威的记述。