‘Swimming’ is a good exercise, here ‘Swimming’ is -

In the sentence "Swimming is a good exercise," the word "swimming" is a gerund. A gerund is a verb form that ends in "ing" and is used as a noun. In this sentence, "swimming" is the subject of the sentence, so it is being used as a noun. A verbal noun is a noun that is formed from a verb. Gerunds, participles, and infinitives are all types of verbal nouns. A participle is a verb form that is used as an adjective. In this sentence, "swimming" is not being used to describe anything, so it is not a participle. An adjective is a word that describes a noun or pronoun. In this sentence, "swimming" is not describing anything, so it is not an adjective. Therefore, the word "swimming" in the sentence "Swimming is a good exercise" is a gerund.