A gerundial noun, also known as a gerund noun, is a noun that is derived from a verb and functions as a noun while retaining its verbal characteristics. It is formed by adding the "-ing" suffix to a verb, turning it into a gerund, and then using it as a noun in a sentence.
For example:
1. "Running" is my favorite form of exercise. In this sentence, "running" is a gerundial noun, functioning as the subject of the sentence.
2. She enjoys swimming in the lake. Here, "swimming" is a gerundial noun, acting as the object of the verb "enjoys."