In addition to a subject, every sentence has a predicate, which asserts or asks something about the subject or tells the subject to do something. The hinge, or key word, of a predicate is the verb. The simple predicate of a sentence consists of the main verb and any auxiliaries (31b); the complete predicate includes the simple predicate plus any modifiers of the verb and any objects or complements and their modifiers.

A compound predicate contains two or more verbs that have the same subject, usually joined by a coordinating or a correlative conjunction.

On the basis of how they function in predicates, verbs can be divided into three categories: linking, transitive, and intransitive.

Linking verbs

A linking verb links, or joins, a subject with a subject complement (sc), a word or group of words that identifies or describes the subject.

If it identifies the subject, the complement is a noun or pronoun (a single mother). If it describes the subject, the complement is an adjective (patient).

The forms of be, when used as main verbs rather than as auxiliary verbs, are linking verbs (like are in this sentence). Other verbs—such as appear, become, feel, grow, look, make, seem, smell, and sound—can also function as linking verbs, depending on the sense of the sentence.

Transitive verbs

A transitive verb expresses action that is directed toward a noun or pronoun, called the direct object (DO) of the verb.

In the preceding example, the subject and verb do not express a complete thought. The direct object completes the thought by saying what he peeled.

A direct object may be followed by an object complement, a word (C) or word group that describes or identifies the direct object. Object complements may be adjectives, as in the next example, or nouns, as in the second example.

A transitive verb may also be followed by an indirect object, which tells to whom or what, or for whom or what, the verb’s action is done. You might say the indirect object is the recipient of the direct object.

Intransitive verbs

An intransitive verb expresses action that is not directed toward an object. Therefore, an intransitive verb does not have a direct object.

The Red Sox persevered.

Their fans watched anxiously.

The verb persevered has no object (it makes no sense to ask, persevered what?), and the verb watched has an object that is implied but not expressed.

Some verbs that express action can be only transitive or only intransitive, but most can be used either way, with or without a direct object.

The verb opened is transitive here.

The door opened silently.

The verb opened is intransitive here.