die Authentizität
authenticity
The quality of being genuine, unaltered, and credible; genuineness.
Ein Experte bestätigte die Authentizität des Gemäldes.
An expert confirmed the authenticity of the painting.

authenticity
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authenticity
The quality of being genuine, unaltered, and credible; genuineness.
Ein Experte bestätigte die Authentizität des Gemäldes.
An expert confirmed the authenticity of the painting.

The noun 'Authentizität' (authenticity) is derived from the adjective 'authentisch' (authentic). The ending '-ität' is typical for abstract nouns that describe a quality and is often used with words of Latin origin.
Die Qualität dieses Produkts ist hoch, aber ich zweifle an seiner Authentizität.
The quality of this product is high, but I doubt its authenticity.
'Authentizität' (authenticity) is often combined with verbs that express checking or confirmation. Typical verbs are 'prüfen' (to check), 'bestätigen' (to confirm), 'anzweifeln' (to doubt), or 'infrage stellen' (to call into question).
Ein Historiker soll die Authentizität des alten Manuskripts prüfen.
A historian is supposed to check the authenticity of the old manuscript.
You can tell from the context whether the genuineness of an object or the sincerity of a person is meant. If it is about art, documents, or products, genuineness is meant. If people are talking about a person's character, it refers to their personal credibility.
Die Authentizität des Kunstwerks wurde von drei Experten bestätigt.
The authenticity of the artwork was confirmed by three experts.
credibility
'Glaubwürdigkeit' and 'Authentizität' both have to do with trust. That is why they can easily be confused. 'Glaubwürdigkeit' mainly asks: Can you believe this person, statement, or source? So it is about reliability and truth. 'Authentizität' is more about asking: Does something seem genuine and not artificial? For people, it can also mean that someone honestly fits with who they are. A news report needs credibility; a performance or a person can seem authentic.

Die Sängerin beeindruckte das Publikum durch ihre Authentizität.
The singer impressed the audience with her authenticity.
Durch die falschen Zahlen verlor der Bericht viel von seiner Glaubwürdigkeit.
Because of the incorrect figures, the report lost much of its credibility.