Defining and Non-defining Relative Clauses

Learn how to give additional information about people and things using relative clauses. Understanding the difference between these clauses is crucial – one gives essential information needed to identify someone/something, while the other just adds extra details.

1. When Do We Use These Clauses?

Defining Relative Clauses (No Commas):

To give essential information that identifies the person/thing

  • The doctor who works at the city hospital is my cousin.
  • Engineers that design buildings must be very precise.


Non-defining Relative Clauses (With Commas):

To give extra information that isn’t essential

  • My sister, who is a lawyer, lives in London.
  • Dr. Smith, who has worked here for 20 years, is retiring.

2. How to Form These Clauses?

Defining Clauses:

  • No commas
  • Who/That/Which + essential information
    • The teacher who speaks five languages works here.


Non-defining Clauses:

  • Use commas
  • Who/Which (never ‘that’) + extra information
    • My boss, who started the company, is retiring soon.

3. Common Relative Pronouns

For People:

  • Who (defining and non-defining)
  • That (only defining)
  • Whom (formal, for objects)

For Things:

  • Which (defining and non-defining)
  • That (only defining)

4. Tips and Mistakes to Avoid

Common Mistakes:

    • My uncle, that is a doctor, lives nearby.
    • My uncle, who is a doctor, lives nearby.
    • The dentist which I visited was excellent.
    • The dentist who I visited was excellent.

Important Tips:

    • If removing the clause changes the meaning → Defining
    • If removing the clause doesn’t change the meaning → Non-defining
    • Never use ‘that’ in non-defining clauses
    • Always use commas with non-defining clauses

3. Examples

Defining Clauses (Essential Information):

  • The nurses who work in emergency care need special training.
  • Teachers that work with young children need lots of patience.
  • The chef who won the competition trained in Paris.


Non-defining Clauses (Extra Information):

  • My brother, who is a successful architect, designed this building.
  • Dr. Johnson, who graduated from Harvard, runs the department.
  • The new manager, who moved here from Spain, starts next week.


Contrasting Examples:

  • Defining: The programmer who sits next to me helps with coding. (Which specific programmer?)
  • Non-defining: Our programmer, who sits next to me, helps with coding. (We only have one programmer)

Scroll to Top