Grammar: Which vs that

Example errors

Look at the example errors below. Can you fix them?

Incorrect
– The university, that has the largest law faculty in the country, recently won an important prize.
– The United Kingdom which has over 60 million inhabitants is one of the largest in Europe.

What are the grammar rules?

1. Which and that can both be used as relative pronouns (in relative clauses), but they are used in different ways. To know which one to use, it is important to understand that there are two kinds of relative clause in English.

2. We use defining (or restrictive) relative clauses to give essential information about someone or something. This information is needed to understand what or who is being referred to.

Here are some examples:

– This is the university that receives the most government funding.
– The tutor who won the award is taking our class today.

You can use either which or that in a defining relative clause to refer to things. However, note that some academic style guides recommend the use of that with defining relative clauses to make it clear that the information is needed to understand what or who is being referred to. This approach also helps you separate defining and non-defining relative clauses in your own mind. Do not use a comma with a defining relative clause.

3. We use non-defining (or non-restrictive) relative clauses to give additional (non-essential) information about someone or something.

Here are some examples:

– Professor Smith, who is my tutor this semester, is very patient and kind.
– The sun, which is almost 150 million kilometres from Earth, is over 4 billion years old.

You must use which in a non-defining relative clause. You must also use a comma. This separates the relative clause from the rest of the sentence, and makes it clear that it is a non-defining relative clause.

4. We also use which to give additional (non-essential) information about an entire clause or idea.

Here’s an example:

– Climate change has been worsening, which has resulted in some action being taken.

5. Here’s a summary of the rules:

Information needed to understand what or who is being referred to

ThingPerson
Try to use that.Use who.
Do not use a comma.Do not use a comma.

Additional (non-essential) information

ThingPerson
Use which.Use who.
You must use a comma.You must use a comma.

Corrected errors

Here are the corrected errors from the start of the lesson.

IncorrectCorrect
– The university, that has the largest law faculty in the country, recently won an important prize.– The university, which has the largest law faculty in the country, recently won an important prize.
– The United Kingdom which has over 60 million inhabitants is one of the largest in Europe.– The United Kingdom, which has over 60 million inhabitants, is one of the largest in Europe.

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