What is a complement?

A complement is any word or group of words that completes the meaning of a subject or object. Technically speaking, direct and/or indirect objects are complements to the transitive verb, in that they complete its meaning. In this sense, a complement is a necessary addition to a sentence for that sentence to have logical sense or meaning.

With this is mind, a complement can be anything that modifies a noun or a verb in the sentence. For example, a simple adjective is technically a complement if it is necessary for the meaning of the noun to be complete:

A car blocked my driveway.

The car blocked my driveway.

The first sentence is complete on its own. No more information is needed because we used the article a, meaning that the car is indefinite and we do not need to know anything about the car. What is important is that it is blocking my driveway.

The second sentence is different; it uses the article the, meaning that it is a specific car that is blocking my driveway, This makes the sentence incomplete because the reader has no way of knowing which car is blocking the driveway. To complete this sentence and give it meaning, we can add an adjective to identify the car:

The neighbour’s car blocked my driveway.

Neighbour’s identifies the car and makes the sentence complete.

This is simple enough. Where writers run into trouble is with longer complements and their positioning. The reason is that complements can look like subjects and objects in that they can be in various forms, such a noun phrase, a clause, an infinitive phrase, and so on.

To identify a part of a sentence as a complement, you will first need to identify the essential elements in the sentence, namely the subject, main verb, and object (if there is one).

Next, find the extra information given and decide what part of the sentence it is completing, and more importantly, if it is necessary to the sentence. In other words, if you can remove it, then it is not a complement, but rather a modifier, something that merely provides “extra” information.

Let’s look at a few examples:

I invited some of my colleagues to my son’s 1st birthday party.

Object = some of my colleagues   complement = to my son’s 1st birthday party

To say only that I invited some of my colleagues does not tell the reader enough information. You can invite colleagues to do something; for example, to ask something, or to go fishing together. You can invite them to your wedding or to a movie or for drinks. In this case, to only say that you invited someone does not convey the full meaning of the action or situation. For this reason we add a complement (in this  case a prepositional phrase) in order to complete the meaning of the sentence.

What is also important to realize is that there are subject complements, object complements, and verb complements.

Subject complements complete the idea of the subject. Sentences that have a be verb as the main verb are followed by a subject complement, not an object:

Zachary is a pilot for United Airlines.

Zachary = a pilot for United Airlines. The complement complete the identity of Zachary in this sentence.

Object complements complete the meaning of the object:

Juan bought a new car to use for his work.

To use for his work complements the object car, which itself is the object to the verb bought. It provides the reader with the purpose of the car. If we merely wrote Juan bought a new car, the reader can guess why; for example, because he won the lottery, or his old one was too small, or any other reason. If the writer wants the reader to understand the complete idea of a sentence, he/ she must complete the sentence for the reader.

A verb complement is any ending that completes the meaning of the verb but that is not an object. In other words, it does not answer the question what? or whom?, but rather answer other questions such as where, when, why, how, etc. We have already learned that sentences come in different forms ( SVO, SVsC, and SVA/P). This last type (SVA/P) is in fact a verb complement type.

Kyle went shopping with his mother.

Shopping completes the meaning of the verb went, by stating where Kyle went. With his mother can be omitted here as it is not necessary, although there might be contexts in which it is necessary:

A: Did Kyle go shopping with his girlfriend?

B: No, he went shopping with his mother.

Here are a few more examples of sentences with complements:

The new Chief of Staff gathered his aides to discuss the changes he envisioned for the department.

to discuss the changes = complement to gathered his aides (infinitive phrase)

(that) he envisioned for the department = complement to changes (adjective clause)

The independent clause, The new Chief of Staff gathered his aide, can stand as a sentence on its own and does not “need” anything else in order to be a complete sentence. However, to have a complete meaning, it requires the added complements.

Dell’s new desktop computer has components that are essential for doing business in today’s highly competitive and technologically integrated markets. (prepositional phrase)

The Arctic region in Northern Canada contains many untapped natural resources that can dramatically change the world’s dependence on oil, most of which is under the control of governments not  necessarily in line with the western world’s ambitions.

Ms. Sheffield aimed to purchase her first home within the first year of her post-university employment, an ambition most of her colleagues found humourous.