Grammar B2 - Non-Defining Relative Clauses

Non-defining relative clauses are used to insert additional background information or flavor into a sentence without interrupting its main flow.

Key concepts regarding these clauses include:

• Non-Essential Nature: The information provided is extra and non-essential. If the clause is removed, the sentence remains grammatically correct and the identity of the subject or object remains clear to the listener.
• The "Comma Sandwich": In writing, these clauses must be enclosed by a "comma sandwich," with one comma placed before the information starts and another placed immediately after it finishes. These commas act as barriers to signal that the content is supplementary.
• Word Choice: Within these clauses, one can use "who" for people, "which" for things, and "whose" for possession. The word "that" should generally not be used because it is too closely connected to the noun.
• Contextual Examples:
  • Using commas in a sentence like "My brother, who lives in London, is a doctor" implies the speaker likely has only one brother, making the location "extra color".
  • Conversely, omitting commas creates a defining clause where the information is necessary to identify which specific person is being discussed.
• Unique Subjects: When referencing something unique—such as "my mother," "the Eiffel Tower," or "Tokyo"—the subject is already identified. Consequently, any subsequent description functions as a non-defining clause and must be wrapped in commas.