What is the primary function of a gerund?

A gerund serves as a verb form that ends in -ing and functions primarily as a noun within a sentence. It can take on roles typically associated with nouns, such as the subject of a sentence, the object of a verb, or the object of a preposition. For example, in the sentence "Swimming is fun," "swimming" acts as the subject and demonstrates how gerunds can embody the characteristics of nouns. This ability to act as a noun is what defines the primary function of a gerund, making it essential in constructing sentences that require such noun-like roles.

The other options refer to different grammatical functions: modifying nouns or pronouns pertains to adjectives, indicating necessity relates more closely to modal verbs, and expressing commands aligns with the use of the imperative mood. None of these accurately capture the unique role of gerunds in sentence structure.