a.

1. 可信的，真实的，可靠的
   The report is authentic.

   这个报告是可靠的。

2. 真正的，非假冒的[Z]
   They found this authentic manuscript of the book from an ancient tomb.

   他们从一个古墓里发现了该书的真正手稿。

3. （依法）有效的，手续齐备的

adj.

1. of undisputed origin or veracity; genuine.
2. Music  (of a church mode) containing notes between the principal note or final and the note an octave higher. Compare with plagal.