Relative clauses are embedded clauses that modify a noun — they add information about who or what the noun refers to. They are introduced by relative pronouns (who, whom, which, that, whose) or relative adverbs (where, when, why). The grammatical choice between these forms depends on whether the noun refers to a person or a thing, whether the clause is defining or non-defining, and whether the pronoun functions as subject or object. These exercises train all those distinctions from B1 to C2 level.
The most important distinction is between defining relative clauses (also called restrictive clauses) and non-defining relative clauses (also called non-restrictive clauses). A defining clause identifies which person or thing the speaker means — it is essential to the meaning of the sentence and is never separated by commas: The student who failed the exam will retake it next month. A non-defining clause adds extra information about a noun that is already uniquely identified — it is enclosed in commas and can be removed without changing the core meaning: My sister, who lives in London, called me yesterday. Getting this distinction right is essential from B1 upwards.
At higher CEFR levels, exercises extend to contact clauses (omitting the relative pronoun when it functions as object: the book I read instead of the book that I read), the formal use of whom, and reduced relative clauses (replacing a relative clause with a participle: the man arrested by police = the man who was arrested by police). These structures appear frequently in academic and formal writing. For the full grammar rules and examples, see the Relative Clauses theory guides.
Frequently Asked Questions
All main relative clause types are covered: defining relative clauses with who, which, that, whose, where, and when; non-defining relative clauses with commas and restricted pronoun use (no that); contact clauses (omitted relative pronoun); whom in formal contexts; and at C1–C2 level, reduced relative clauses using participle phrases.
Use who for people: the teacher who helped me. Use which for things and animals (in formal English): . Use for both people and things in : . In , cannot be used — only or : .
the book which I read
that
defining clauses only
the house that I grew up in
non-defining clauses
that
who
which
My car, which is ten years old, still runs well
Start at B1 for basic defining relative clauses with who/which/that. Choose B2 for non-defining clauses, whose, where, when, and contact clauses. Start at C1–C2 for formal whom, reduced relative clauses, and relative clauses in academic writing. If you are unsure of your level, take the free Level Test.
A contact clause is a relative clause from which the relative pronoun has been omitted. This is possible only when the relative pronoun functions as the object of the clause, not the subject. Compare: The film that I watched was brilliant (with pronoun) and The film I watched was brilliant (contact clause — pronoun omitted). When the relative pronoun is the subject, omission is not possible: The man who called me was a doctor — you cannot say The man called me was a doctor.