In Grammar 9-1 and 9-2 we saw many examples of relative clauses. However, most of them reflected one type of clause: Defining Adjective Clause. We also have Non-Defining Adjective Clauses. In this lesson, we’ll look at each one and see what the differences are.

A Defining Adjective Clause is a necessary part of a sentence, as it defines which noun the speaker is referring to.

  • The man who sat down was Mike. (Defining Adjective Clause)

In this sentence, you can't omit "who sat down." It defines which man.

A Non-Defining Adjective Clause is extra information in a sentence. The noun the speaker is referring to is clear, so the information is not necessary for the meaning of the sentence.

  • The man, who I had never met before, was looking at me strangely. ( Non-Defining Adjective Clause).

In this sentence, you can omit "who I had never met before." It does not define which man, so it is simply extra information.

Relative Pronouns Used

Defining Adjective Clauses

For people

  • who
  • that
  • X

For things

  • which
  • that
  • X

Non-Defining Adjective Clauses

For people

  • who

For things

  • which

As we studied in Grammar 9-1, it is sometimes possible to omit relative pronouns in some Defining Adjective Clauses, especially in spoken English, if the relative pronoun is an object. However, in Non-Defining Adjective Clauses, relative pronouns are always necessary.

  • My friend who / that / X I met in Canada loves to try new food.
  • I wrote the report which / that / X I submitted last week.

  • Correct

    Anne Giroux, who I met in Quebec City last year, is giving a lecture on sustainable farming next month.

  • Incorrect

    Anne Giroux, I met in Quebec City last year, is giving a lecture on sustainable farming next month.

Information

Defining Adjective Clauses give us information that is necessary to understand the person, thing or place it is describing.

  • My friend who / that is from Canada loves to try new food.
  • I wrote a report which / that was about the Canadian healthcare system.

Non-Defining Adjective Clauses give us extra information that is not necessary to understand the person, thing or place it is describing.

  • My friend John, who is from Canada, loves to try new food.
  • The report, which is on the table, was completed yesterday.

Which is more common?

Defining Adjective Clauses are more common in spoken English. Non-Defining Adjective Clauses are more formal and common in writing. In speaking, we usually say two sentences instead of one sentence with a Non-Defining Relative Clause.

Spoken

  • My friend John loves to try new food. He's from Canada.

Written

  • My friend John, who is from Canada, loves to try new food.

Punctuation

From the examples above, you can see that in writing we use commas to distinguish between the two types of relative clauses. In Non-Defining Adjective Clauses, we use commas; in Defining Adjective Clauses, we don’t.

If we use Non-defining clauses when speaking, the commas represent a pause in our speech.

  • The spices, (pause) which I bought yesterday, (pause) were imported from India.
  • David, (pause) who is sitting over there, (pause) works as a nutritionist.

Exercise

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