English grammar: Relative clauses (defining and non-defining)

What this grammar point covers

Relative clauses are parts of a sentence that give more information about a noun. They usually start with words like 'who', 'which', or 'that'. There are two types: defining (necessary information) and non-defining (extra information).

When to use it

Use relative clauses in English to give more details about a person or thing. Defining clauses tell us which person or thing you mean. Non-defining clauses add extra information that is not necessary to understand the main idea.

Key forms

• 'who' for people: The man who lives next door is friendly.
• 'which' for things/animals: The book which is on the table is mine.
• 'that' for people or things (defining clauses only): The car that I bought is red.
• Non-defining clauses use commas: My sister, who lives in Paris, is coming to visit.

Examples

Tips

• Do not use 'that' in non-defining relative clauses (with commas).
• Remember to use commas for non-defining clauses, but not for defining clauses.
• 'Who' is for people, 'which' is for things and animals, 'that' is for people or things (in defining clauses).

Exceptions and edge cases

• In spoken English, 'that' is often used instead of 'who' or 'which' in defining clauses.
• Sometimes the relative pronoun can be omitted in defining clauses: 'The book (that) I read was interesting.'