A non-finite verb is a type of verb that cannot act as the predicate of a sentence, because it does not describe the action of the subject. There are three basic types of these verbs including participles, which are verbs that act as an adjective within a sentence and often end in the suffix “-ing.” Infinitive verbs are also non-finite and typically include the auxiliary verb “to” such as “to run” or “to go.” There is also a type of non-finite verb referred to as a gerund, which is a verb in the “-ing” form that acts as a noun or as part of a noun phrase in a sentence.
Also called a “verbal,” non-finite verbs are different from finite verbs in that they have no restrictions defining the forms they take. This does not mean there are no rules governing their use, but that finite verbs are restricted by different tenses and forms to allow them to function as predicates within a sentence. A basic finite verb is a word like “ran” in the sentence “The cat ran quickly,” which acts as a predicate for the subject “The cat.” In contrast to this, a non-finite verb often acts in another form within a sentence, though it can be part of a predicate verb phrase when in the infinitive form.
One of the most common ways that a non-finite verb can appear is as a participle. This is a verb that effectively behaves like an adjective within a sentence and describes a particular noun or pronoun. In a sentence like “That is my walking stick,” the word “walking” is a non-finite verb that describes the “stick.” This is a verbal in the form of a participle. Another example of this would be the verb “flying” in the sentence “I was in my flying machine.”
A non-finite verb can also refer to infinitive forms of verbs, which are their most basic form in a language. In English, the infinitive form is usually accompanied by the auxiliary verb “to” such as “to go” or “to run.” These verbs can be part of the predicate in a sentence, when part of a verb phrase such as “I have to run across the street,” in which “have” is in the finite form. There is a common rule in English against a “split infinitive” in which the infinitive is separated from its auxiliary, such as the phrase “to boldly go.” Many grammarians and linguists argue about this issue, however, though it is typically best to avoid a split infinitive for scholarly or professional writing.
Gerunds are the third type of non-finite verb in English, which are verbs that behave like nouns and have an “-ing” ending. In the sentence, “Teaching is a noble profession,” the word “Teaching” acts as a noun and is the subject of the sentence. Gerunds can be subjects, objects, and the subject of a prepositional phrase, much like any other noun. They are also commonly part of a gerund phrase, which acts like a noun phrase, such as the phrase “Running in the morning,” in the sentence “Running in the morning is good for your health.”