* Gerunds are verb forms ending in "-ing" that act as nouns. They describe actions or states of being.
* Noun substitutes take the place of nouns in a sentence. This means they can act as the subject, object, object of a preposition, or even the complement of a verb.
Here are some examples:
* Subject: Swimming is my favorite exercise. (Swimming replaces the noun "activity")
* Object: I enjoy reading novels. (Reading replaces the noun "activity")
* Object of a preposition: He is good at playing the guitar. (Playing replaces the noun "skill")
* Complement of a verb: His favorite hobby is hiking. (Hiking replaces the noun "hobby")
Key takeaway: Gerunds are versatile and can act as noun substitutes in various grammatical contexts. They offer a concise way to express actions or states of being without using full noun phrases.