1. The genuine, original, or true version of something; a form that is verified as legitimate and not counterfeit
The museum displays the authentic form of the ancient manuscript.
O museu exibe a forma autêntica do manuscrito antigo.
2. In legal or official contexts, the original or certified version of a document
The contract must be signed in its authentic form to be valid.
O contrato deve ser assinado em sua forma autêntica para ser válido.
3. The true or natural expression of something without alteration or falsification
She expressed her emotions in their authentic form.
Ela expressou suas emoções em sua forma autêntica.