What does "authenticity" mean?

The quality of being genuine or not corrupted from the original, of having the same origin (or attribution, commitment, intention, etc.) as claimed.

How do you pronounce "authenticity"?

Pronounced //ɑθɛnˈtɪsɪti//.

Common synonyms include: genuineness, legitimacy, absolute realism, accomplished fact, actuality, artlessness.

/ɑθɛnˈtɪsɪti/ noun

noun ·Moderate ·High school level

Noun

1
The quality of being genuine or not corrupted from the original, of having the same origin (or attribution, commitment, intention, etc.) as claimed. uncountable, usually
"I hereby certify the authenticity of this copy."
2
undisputed credibility wordnet
3
The quality of being authentic (of established authority). obsolete, uncountable, usually

"I doubt the authenticity of the document."

From authentic + -ity.