Complementizers make a clause into the subject or object of a sentence. In this lesson, we will learn all about them.

Complementizers in the English Grammar

What Are Complementizers?

Complementizers are often used to introduce clauses that function as the subject, object, or complement of the main verb in a sentence. They can also be used to introduce dependent clauses that express a condition, concession, or reason for an action or event.

Complementizers: Types

Complementizers can introduce:

Complementizers Introducing a Relative Clause

Relative complementizers are used to introduce a dependent relative clause, which modifies a noun or pronoun in the main clause of a sentence. The relative clause provides additional information about the noun or pronoun that it modifies, helping to clarify its meaning. They can be relative pronouns or relative adverbs.

Relative Pronouns

I like girls who are pretty.

He likes action movies that are exciting.

Relative adverbs used as complementizers

Relative Determiners

Unlike other relative complementizers, 'whose' only appears as a determiner before a noun, rather than standing alone as a pronoun.

This is the woman whose house has burned down.

Solar energy is an idea whose time has come.

Relative Adverbs

I remember the day when he proposed to me.

This is the hospital where my mom gave birth to me.

Complementizers Introducing a Nominal Clause

Nominal complementizers are used to introduce a nominal relative clause that functions as an object, subject, or complement in a sentence. They can be either relative pronouns or relative adverbs, such as:

I read whatever is available.

It's not what you said, it is how you said it.


The complementizer always appear at the beginning of a complement phrase.

Complementizers Introducing a Subordinate Clause

Subordinating conjunctions can function as complementizers, introducing a subordinate (also called embedded) clause within a sentence. There are many subordinating conjunctions in English, such as:

I am going to have problems quitting my job even if I find a better one.

We didn't enjoy the day because the weather was so awful.

The Empty Complementizer

In some contexts, we can omit the complementizer 'that'. For example:

I wish that I didn't have to go to work today. → I wish I didn't have to go to work today.

The result is called a null (or empty) complementizer. The relative complementizer can only be omitted when it is the object of the clause. When it is the subject of the clause, it cannot be omitted. Pay attention to the examples:

The man (who) my friend saw in the street was my uncle Jim.

John is my friend who is wearing jeans.


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