* Abstract nouns represent concepts, qualities, ideas, or feelings that you can't physically touch or see.
* "Interesting" describes a feeling or quality that something possesses. It's not a tangible thing.
Example:
* "The book was full of interesting facts." Here, "interesting" is the quality of the facts.
However, "interesting" can also be used as an adjective:
* "The book was an interesting read." Here, "interesting" describes the book.
In summary, "interesting" can be an abstract noun depending on how it's used in a sentence.