What is the abstract noun for frank?

There isn't a single perfect abstract noun for "frank." However, depending on the context, you can use these options:

* Frankness: This is the most direct translation, meaning open and honest communication.

* Candor: This emphasizes honesty and sincerity, often in a way that is brave or forthright.

* Openness: This emphasizes the lack of secrecy or deception.

* Honesty: This is the most general term for truthfulness.

* Directness: This emphasizes the lack of ambiguity or circumspection.

The best choice will depend on the specific nuance you want to express.