While not one of the traditional eight parts of speech in the English language, a gerund is a specific type of word applied to English grammar. The word stems from a verbal, or a verb form, but does not act as a verb in a sentence. There are three types of verbals: gerunds, participles, and infinitives. Though a gerund is formed from a verb and indicates an action or state of being, it acts as a noun and therefore occupies a place in a sentence where a noun normally would, such as a subject, a direct object, or an object of a preposition.
Without exception, a gerund always ends in –ing. It may be confused with a participle, which is a verbal that most often ends in -ing or -ed, but a participle acts as an adjective modifying a noun rather than a noun itself. The following words ending in -ing could be gerunds or participles, depending on how they are used in a sentence.
While gerunds can be difficult to identify in some sentence structures, readers can remember that they are always used as nouns and always end in -ing. The following sentence is an example where the word sleeping is a gerund complementing the subject: My dog's favorite pastime is sleeping.
In this example, "sleeping" acts as a compliment to the subject. It identifies what the pastime is rather than what the dog is doing. In a different but similar sentence, a noun could replace sleeping as a subject compliment: My dog’s favorite toy is a ball.
A gerund phrase is a group of words that contains a gerund and also functions as a subject, object, or indirect object. The other words modify or compliment the expressed action or state of being that the gerund word is based on. When constructing sentences with these verbals, the gerund or phrase rarely, if ever, requires punctuation.