Authentic (adjective)

1. Genuine and not counterfeit.
2. Representing one's true nature or beliefs; true to oneself.

Origin:

Early 17th century: from french authentique or latin authenticus, from greek authentikos, from authentes "author".

Examples:

1. The painting was authenticated as a Rembrandt.
2. The coin was determined to be authentic.
3. The restaurant served authentic Chinese food.
4. The document was found to be an authentic copy of the original.
5. She felt more authentic when she started to express herself honestly.