Definition:

A gerund is a verb form that functions as a noun. It is derived from the Latin gerundium, which is derived from the Latin verb gerundus, meaning "to carry on, to pursue."

Functions of gerund in english: 

• The function of a gerund is to name an activity or to serve as the object of a preposition.

For example, in the sentence "I like swimming," the word "swimming" is a gerund and functions as the direct object of the verb "like."

• When a gerund is used as the subject of a sentence, it is usually in the form of "ing" + verb. For example, "Swimming is my favorite activity." In this sentence, "swimming" is the gerund and functions as the subject.
• When a gerund is used as an indirect object, it usually takes the form of "to" + verb. For example, "I gave swimming a try." In this sentence, "swimming" is the gerund and functions as the indirect object of the verb "gave."
• When a gerund is used as the object of a preposition, it usually takes the form of "verb + ing." For example, "I'm looking forward to swimming." In this sentence, "swimming" is the gerund and functions as the object of the preposition "forward."

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Conclusion

Gerunds are verb forms that function as nouns. 

Gerunds can be used as the subject or object of a sentence.

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