Definition from Wiktionary, the free dictionary
- The quality of being genuine or not corrupted from the original.
- I hereby certify the authenticity of this copy.
- Truthfulness of origins, attributions, commitments, sincerity, and intentions.
- The authenticity of this painting is questionable.
- (obsolete) The quality of being authentic (of established authority).
- (quality of being genuine): genuineness
Related terms 
the quality of being genuine or not corrupted from the original
truthfulness of origins