Subject, Verb, Object, and Complement: What They Do and Why They Matter in TOEFL

Summary of Four Sentence Elements

Here is a quick summary of the four basic sentence elements: subject, verb, object, and complement.

We will explore this topic in more detail later in this article, but the table below briefly shows the difference between a sentence with an object and one with a complement.

Grammatical Knowledge and the New TOEFL

In the new TOEFL test format, grammatical knowledge plays a more important role than it did in the previous version. A higher level of grammatical accuracy is required, especially in the Reading and Writing sections, where a clear understanding of sentence structure can make these tasks much easier.

This is particularly true in Writing Section Part 1. In this task, you are asked to arrange words from a word bank to form a complete and meaningful sentence. To do this successfully, you need to be comfortable with basic English grammar. Without that foundation, it becomes difficult to determine the correct word order with confidence.

For this reason, having a solid grasp of basic grammar is essential for the new TOEFL. It allows you to approach these questions logically rather than relying on guesswork. In this article, we focus on four fundamental grammatical components: subject, verb, object, and complement. These elements appear in virtually every grammar-based question and form the foundation for understanding sentence structure in the new TOEFL.

Five Sentence Construction of English

Note that most of the English sentence falls into one of five sentence construction:

• SV (Subject-Verb)
• SVC (Subject-Verb-Complement)
• SVO (Subject-Verb-Object)
• SVOO (Subject-Verb-Indirect Object-Direct Object)
• SVOC (Subject-Verb-Object-Complement)

When a sentence fits into one of these patterns, it is grammatically complete and meaningful. Understanding these sentence structures is especially useful for Writing Section Part 1, where you are required to determine the logical order of words taken from a word bank.

Four Sentence Constituents

We will explain how each sentence pattern works in detail in a separate article. In this article, however, the focus is on the core components that make up these structures: subject, verb, object, and complement.

Subject

In an active sentence, the subject represents the doer of an action or the main topic described in the sentence. One key rule is that only a noun, noun phrase, gerund, or gerund phrase can function as the subject. In many cases, the subject appears before the verb.

Let’s look at how the subject works in the example sentences below.

My teacher wants my classmates to study harder.

In this sentence, “my teacher” is the subject, and the verb is “wants.” Because the subject represents the doer of the action, we understand that it is the teacher who wants something. In other words, “my teacher” wants “my classmates to study harder,” not the classmates wanting something themselves. Since the object “my classmates” comes after the verb, we can identify this sentence as following the SVO sentence pattern.

Here’s another sentence.

Joe is my best friend.

In this sentence, the proper noun “Joe” functions as the subject, followed by the verb “is” and the complement “my best friend.” This sentence follows the SVC sentence pattern.

When a sentence follows the SVC pattern, the subject is not the doer of an action. Instead, the subject is described by the complement. In this case, “Joe” is not doing anything; rather, the sentence explains who “Joe” is. In other words, “Joe” serves as the topic being described, not as an agent performing an action.

Verb

Among the four sentence components, the verb is perhaps the easiest to understand. In general, a verb represents an action performed by the subject.

However, some verbs, such as “seem” and “be,” are difficult or impossible to associate with a concrete action. The primary function of these verbs is to connect the subject with a complement. For this reason, they are collectively called linking verbs.

Identifying the main verb in a sentence is especially important when reading sentences that contain long modifiers or additional clauses. As mentioned earlier, the element that comes before the main verb is the subject. Keeping this relationship in mind helps you locate the core structure of a sentence more easily.

Let’s look at how the verb functions in the following example:

An article about the benefits of daily exercise encourages me to walk at least 30 minutes a day.

You may notice that the main verb in this sentence is “encourages.” Once the main verb is identified, we can determine that everything before it functions as the subject. Although it is relatively long, “An article about the benefits of daily exercise” is the subject of the sentence. More specifically, the core of the subject is “an article.”

After identifying the core subject, you can temporarily ignore the additional information attached to it. This often makes sentence interpretation much easier. Consider the following two sentences:

• An article encourages me to walk at least 30 minutes a day.
• An article about the benefits of daily exercise encourages me to walk at least 30 minutes a day.

The first sentence is clearly easier to process. However, the core meaning does not change even though the descriptive phrase modifying the subject is removed. This technique of focusing on the core subject and verb can help you understand complex sentences more efficiently.

Let’s see another example.

My father gave me his wallet.

This sentence follows the SVOO sentence pattern, in which two objects come after the verb. We will examine this structure in more detail later in the article. For now, let’s focus on identifying the verb, which is “gave.” Again, once the verb is identified, we can see that everything before it functions as the subject. In this case, “my father” is the subject of the sentence.

Object

In contrast to the subject, the object represents a person or thing that is affected by the verb. This explanation applies to most active sentences. In the passive voice, the relationship between subject and object is reversed.

Because the object must be something influenced by the action, only a noun, noun phrase, gerund, or gerund phrase can function as an object. Let’s look at the example below.

I kicked the ball.

In this simple sentence, “the ball” is the object because it’s affected by the verb “kicked.” As discussed earlier, the subject is the doer of the action, so “I” is the one who kicks the ball in this sentence.

Complement

While many people are already familiar with the concepts of subject, verb, and object, the idea of a complement often remains unclear. This confusion partly comes from the fact that both complements and objects are frequently expressed using nouns. However, despite this surface similarity, complements and objects play very different grammatical roles.

A complement can be understood as a word or phrase that describes the state, identity, or condition of the subject. For this reason, both nouns and adjectives can function as complements, depending on the sentence structure.

Distinguishing a Complement from an Object

One practical way to distinguish a complement from an object is to pay attention to the verb that comes before it.

In many cases, if the verb clearly expresses an action that can be imagined, it’s likely followed by an object. On the other hand, if it’s difficult or impossible to picture a concrete action associated with the verb, that is often a sign that the verb is followed by a complement.

For example, “be” is a typical linking verb that takes a complement and forms an SVC structure, as in “She is my mother.” Can you imagine any concrete action represented by the verb “is” in this sentence? Of course not. The verb doesn’t describe an action; instead, it simply links the subject to information that identifies or describes it.

Verbs that describe a person’s state or condition also tend to be followed by a complement. A well-known example is “seem.” Compared with “be,” it may appear more verb-like at first glance. Even so, it still does not represent a concrete or observable action. Because there is no clear action to imagine, verbs like “seem” are followed by a complement rather than an object.

Complement in Sentences

My father is my teacher.

• Subject: My father
• Verb: is
• Complement: my teacher

This sentence clearly follows the SVC structure: “my father” functions as the subject, “is” as the linking verb, and “my teacher” as the complement. In this sentence, the complement describes who my father is, referring to his role or position rather than an action he performs.

Joe is sad.

• Subject: Joe
• Verb: is
• Complement: sad

This sentence is another example of the SVC structure. In this case, the complement “sad” is an adjective rather than a noun. The subject and the complement are linked by the verb “is.” This shows that the SVC structure can also be used to describe the subject’s emotional or mental state, not just identity or role.

I feel sick.

• Subject: I
• Verb: feel
• Complement: sick

In this sentence, it’s difficult to imagine any concrete action associated with the verb “feel.” This is a strong indication that the verb is followed by a complement rather than an object. Indeed, “feel” is a verb that describes the subject’s state of being, which is why it commonly takes a complement.