What you'll learn
By the end of this lesson, you'll be able to add extra, non-essential information about a person or thing using commas, who and which.
When do I use it?
A non-defining relative clause adds extra information about someone or something that is already identified. The main sentence still makes sense without it, and the clause is separated by commas:
- "My brother, who lives in London, is visiting us." (We already know which brother — the fact he lives in London is extra.)
- "Paris, which is the capital of France, is beautiful."
You cannot use that here, and you cannot drop the pronoun:
- "This car, that is very fast, is expensive." — wrong. Use which.
- "The Eiffel Tower, was built in 1889, is famous." — wrong. The pronoun is essential.
How do I form it?
noun, + who / which + clause, + main sentence
- Our neighbour, who is 80, still runs every day.
- The new café, which opened last month, is always full.
- Professor García, whose book I read, will give a talk.
- Spain, where my family is from, is in southern Europe.
Compare with a defining clause: "The cars which are red are mine" (essential — tells you which cars) vs "My car, which is red, is parked outside" (extra — I have one car).
Common mistakes for Spanish speakers
In Spanish, "mi hermano, que vive en Londres" is natural, but speakers often drop the pronoun in English ("my brother, lives in London, is visiting") or use "that" instead of who/which ("my sister, that lives in Madrid"). In a non-defining clause the pronoun can NEVER be omitted and "that" is not allowed for people or things. Also keep the comma placement: the clause is extra, so it sits between commas.
Already know who/what? → commas + who/which/whose/where. No "that", no dropped pronoun.
Practice
Multiple Choice
B1Which sentence is correct?
Fill in the Blank
B1My sister, works in Barcelona, is coming this weekend.
Hint: People take 'who' in a non-defining clause.
Find the Error
B1Word Order
B1Put the words in order to make a sentence with a non-defining clause
Practice Speaking
Apply what you've learned in a real conversation with AI feedback.
Level: B1