Blog about English
Using relative clauses to add extra, non-essential information.
A non-defining relative clause adds extra information about a person, thing, or situation that is already sufficiently identified.
The information is additional rather than necessary for identifying the noun. For example, My brother, who lives in London, is visiting us.
A non-defining relative clause is separated from the main clause by commas.
For example, My sister, who lives in Paris, is a doctor.
A defining relative clause identifies which person or thing is meant, while a non-defining clause provides additional information about an already identified noun.
Compare The students who passed the exam received certificates with The students, who passed the exam, received certificates.
Who is commonly used for people in non-defining relative clauses.
For example, My uncle, who lives nearby, visits us often.
Which is commonly used for things in non-defining relative clauses.
For example, The house, which was built in 1920, has recently been renovated.
That is not normally used to introduce non-defining relative clauses.
Use who or which instead. For example, My car, which is five years old, still works well.
Whom can be used as the object of a non-defining relative clause referring to a person, especially in formal English.
For example, Mr Brown, whom I met yesterday, will lead the meeting.
Whose can introduce a non-defining relative clause expressing possession.
For example, Jane, whose brother lives abroad, is moving next month.
A relative pronoun in a non-defining relative clause is normally required, even when it functions as the object.
For example, My teacher, whom I met yesterday, was very helpful. The pronoun is not normally omitted.
Proper names can be followed by non-defining relative clauses because the person or place is already identified.
For example, Anna, who lives in Rome, is visiting next week.
Nouns referring to unique or already identifiable entities can be followed by non-defining relative clauses.
For example, The sun, which is a star, provides Earth with energy.
Possessive noun phrases can be followed by non-defining relative clauses when the noun is already clearly identified.
For example, My old car, which I bought in 2018, is still reliable.
Which can refer not to a single noun but to the situation or event described by the preceding clause.
For example, He missed the train, which meant that he was late for work.
A non-defining which-clause can comment on or evaluate an entire preceding statement.
For example, She passed the exam, which surprised everyone.
Which is used for things in non-defining clauses, while that is generally restricted to defining relative clauses.
For example, The car, which I bought recently, is already having problems.
Prepositions can appear before the relative pronoun in formal English or at the end of the clause in less formal English.
For example, The person to whom I spoke was helpful and The person who I spoke to was helpful.
A preposition can be placed directly before whom or which in formal English.
For example, The company for which she works is expanding.
Where can introduce a non-defining relative clause referring to a place.
For example, Oxford, where she studied, is a historic university city.
When can introduce a non-defining relative clause referring to a time or period.
For example, 2020, when many businesses moved online, changed working habits.
Whose can refer to possession in a non-defining clause involving people, organizations, and some things.
For example, The company, whose offices are in London, is hiring new employees.
Non-defining relative clauses allow additional information to be inserted without changing the main identification of the noun.
They are especially useful for adding background facts, descriptions, explanations, and comments.
Non-defining relative clauses are common in formal and academic writing for adding concise background information.
For example, The study, which was conducted over five years, produced significant results.
Non-defining relative clauses are also common in conversation, especially when adding explanatory or descriptive information.
For example, My brother, who lives in Canada, is coming to visit us.
Commas should clearly mark the beginning and end of a non-defining relative clause.
Incorrect punctuation can change whether information appears essential or additional.
Use commas, appropriate relative pronouns, and correct clause structure in non-defining relative clauses.
Common mistakes include using that, omitting the relative pronoun, omitting commas, and treating additional information as if it were essential identifying information.