How to Use Relative Clauses in English
Table of Contents
What Are Relative Clauses?
Relative clauses are parts of a sentence that give extra information about a person, thing, place, or idea. They help make our meaning more specific and remove confusion. Without them, our sentences can sound too general, leaving the listener unsure what or who we mean.
For example, if I show you a photo with a hundred people and say, He is my brother or The boy is my brother, you probably won’t know which person I’m talking about. It’s not specific enough. But if I say, The young boy who is wearing a blue T-shirt is my brother, the picture becomes clear and you know exactly who I mean.
This also applies to objects. If I ask, Where is the book? or Where is it?, you may not know which book I’m referring to. Instead, I could say, Where is the book which I gave you last week? Now it’s clear which book I’m talking about.
Relative clauses can also help avoid making misleading statements. For instance, if I say, I don’t like people, it sounds like I dislike everyone, which isn’t true. I can be more accurate by saying, I don’t like people who throw trash on the street, I don’t like people who don’t pick up after their dogs, or I hate the guy who keeps leaving dog poop on my lawn (true story).
By adding these extra details, relative clauses make our sentences more precise, informative, and easy to understand.
WHO
We use who in relative clauses when we are talking about people. It helps us add more details about the person so the listener knows exactly who we mean. This is useful when we are describing someone’s appearance, actions, their job, or anything else about them.
The boy who came here yesterday was my high school friend.
The boy who came here yesterday is my neighbor.
In both sentences, who came here yesterday gives extra information about the boy. Without it, the sentence would be less specific.
We can also combine two separate sentences into one using who.
The boy came here yesterday. He is my neighbor. → The boy who came here yesterday is my neighbor.
Keep in mind that we are replacing “he” with “the boy who came here yesterday,” so we do not repeat “he” in the sentence. It would be incorrect to say “The boy who came here yesterday he is my neighbor,” because that’s essentially like saying “he he is my neighbor.”
The tense inside the relative clause can be different from the tense in the main sentence.
The boy who came here yesterday (past simple) will come back next week (future simple).
The boy who came here yesterday (past simple) is now washing his car (present continuous).
The boy who comes here every day (present simple) was sitting in his car yesterday (past).
The boy who comes here every day (present simple) works as a doctor (present simple).
The boy who is coming here right now (present continuous) was in Canada last year (past simple).
The boy who was coming here last week was stopped on his way by the police.
We can also describe jobs using who:
She is a teacher who works at the local school.
I know a doctor who specializes in heart surgery.
I know a teacher who writes articles about grammar.
I like people who are disciplined and try to learn new things all the time.
In these cases, we are replacing “him” or “them,” not “he” or “they.”
If the relative clause referred to the subject, the last two sentences would be:
The teacher who writes articles about grammar ( = subject / he / the boy) has a lovely dog.
The people who are disciplined and try to learn new things ( = subject / they / the people) usually become successful.
In many cases, we can use that instead of who, especially in everyday conversation:
The boy that came here yesterday is my neighbor.
I don’t like people that throw trash on the street.
She is a teacher that works at the local school.
Both who and that are correct when talking about people, but who is often preferred in more formal writing.
WHICH
Which is used to give extra information about things, objects, or animals, rather than people. It often helps to clarify or specify which item or group we are talking about. Unlike who, it doesn’t refer to a person. Who replaces people and refers to subjects like “he,” “she,” “they,” or “someone.” Which replaces things, objects, or animals and usually refers to “it” or “they” (for things).
Examples:
The book which/that I borrowed from the library is fascinating.
I bought a car which/that has excellent fuel efficiency.
She showed me a picture which/that her friend had taken during their trip.
We visited the museum which/that was built in the 18th century.
I can’t find the pen which/that I left on the desk.
WHEN
When is used in relative clauses to give more information about a time. It replaces references like “that day” or “the time” and makes your sentence more specific.
Examples:
The day when/that we met was unforgettable.
I remember the year when/that I first visited Paris.
That was the moment when/that everything changed.
He couldn’t forget the night when/that he won the competition.
She’ll never forget the morning when/that she got her first job offer.
The week when/that it rained nonstop was exhausting.
Do you recall the time when/that we went hiking in the mountains?
WHERE
Where is used in relative clauses to give more information about a place. It replaces references like “that place” or “the location” to make your sentence clearer.
Examples:
The park where we had our picnic was beautiful.
I visited the city where my grandparents were born.
That’s the restaurant where we celebrated her birthday.
He couldn’t forget the town where he spent his childhood.
She showed me the house where she grew up.
The school where I studied had a huge library.
Do you remember the café where we first met?
WHOSE
Whose is used in relative clauses to show possession. It replaces possessive pronouns like “his,” “her,” “their,” and links the noun being described to something that belongs to them. Unlike the previous categories, whose cannot be replaced by “that”.
I met a boy who used to work here.
I met a boy whose father used to work here.
Explanation: The first says that I met a boy. The boy works here.
The second sentence says that I met a boy. The boy does not work here. The boy’s father works here.
More examples:
The woman whose car was stolen reported it to the police.
He is a writer whose books are translated into many languages.
They have a friend whose brother lives in Canada.
She spoke to a teacher whose students always perform well in exams.
I saw a dog whose tail was wagging happily.
We visited a museum whose exhibits date back hundreds of years.
The student whose homework was late apologized to the teacher.
WHY
We use why as a relative pronoun to explain a reason or purpose for something. It usually refers back to a noun like reason or explanation. For example, if you say, “I don’t understand the reason,” it’s not specific. Adding a relative clause with why makes it clear: “I don’t understand the reason why she left early.”
Other examples:
The teacher explained the reason why the assignment was late.
I know the reason why he is upset.
Can you tell me the reason why they cancelled the event?
She couldn’t explain the reason why her computer stopped working.
He didn’t reveal the reason why he resigned.
I still don’t understand the reason why this happened.
WHOM
Whom is a relative pronoun that can replace who in certain situations. It has almost the same meaning as who, but it is considered more formal or old-fashioned in modern English.
Whom can be used when the relative pronoun functions as the object of the clause, not the subject. In other words, if the wh- word is followed by a verb, it cannot be replaced with whom, but if it’s followed by a person or thing, it can.
Examples:
The person who drives to work every day is my neighbor. (Here, who is the subject of the clause, so whom cannot be used.)
The person who/whom I saw yesterday is my cousin. (Here, whom is the object of “I saw,” so it is correct.)
She is the student who/whom the teacher praised. (Object of “praised”)
The man who called you is waiting outside. (Subject, not whom)
The man who/whom you called is on the line. (Object of “called”)
WHAT
What isn’t technically a relative clause, but it can act in a similar way by introducing a clause that refers to a thing or idea. Essentially, it means “the thing that” or “the things that.”
You can use what when you don’t have a specific noun to refer back to: “I don’t know what to say.” You cannot use what if you already have a clear noun; in that case, use that or which instead: “I don’t like the book that you gave me.” It would be incorrect to say “I don’t like the book what you gave me.”
Examples:
I don’t understand what he wants.
Take what you need and leave the rest.
She gave me what I asked for.
Do you know what happened at the meeting?
I love what this restaurant serves.
He explained what we should do next.
Tell me what you think about this plan.
They decided what was best for the project.
That’s what she said! XD
Examples from the TOEFL Test
Question 1
The following example is designed for TOEFL Reading Practice Test #6 – The Pit Organs of Snakes.
Reading Passage: Interestingly, a rattlesnake only targets warm-blooded prey, and if the prey is at room temperature, the snake will not strike. However, a blindfolded snake will accurately strike at a dead rat that is warmer than its surroundings when it is pulled across the cage. Since the snake cannot rely on vision due to the blindfold, and still strikes accurately at objects like a moving, cloth-wrapped electric bulb, it is evident that the pit organs are responsible for detecting the heat of warm objects. All snakes with pit organs prefer to feed on warm-blooded prey, further supporting the belief that these organs function as infrared detectors. In rattlesnakes, the pit organs are positioned between the nostrils and eyes, one on each side, and are connected to numerous nerves, suggesting a sensory role for these organs.
Question: Why does the writer mention a dead rat that is warmer than its surroundings?
A. To show that snakes can hunt successfully without relying on sight.
B. To prove that snakes are only interested in live prey.
C. To argue that snakes use sound and vibration to detect prey.
D. To demonstrate that snakes depend on smell when hunting in darkness.
Correct Answer: A
Explanation: The writer introduces the example of a blindfolded snake striking at a dead rat that is warmer than its surroundings to emphasize two key points. First, the rat being dead eliminates movement as a possible cue, meaning the snake is not responding to motion. Second, the rat being warm shows that temperature, not life or activity, triggers the strike. Because the snake is blindfolded and the prey is motionless, the only remaining explanation is that the snake detects the heat contrast, proving the function of the pit organs. The key phrase is “Since the snake cannot rely on vision due to the blindfold, and still strikes accurately… it is evident that the pit organs are responsible for detecting the heat of warm objects.”
Option B is incorrect because the snake still strikes at dead prey, so “life” is not the factor. Option C is wrong because the passage specifically states that sound and vibration have no effect on nerve activity. Option D is incorrect because smell is never mentioned as a factor in this context.
Question 2
The following example is designed for TOEFL Reading Practice Test #23 – Coevolution of Pinyon Pines and Pinyon Jays.
Reading Passage: Organisms of different species frequently evolve adaptations that make them utterly and specifically dependent on each other for resources. For example, many trees must have mycorrhizal fungi living in their root systems, fungi that are indispensable to the tree because they facilitate mineral uptake from the soil. In turn, the fungi rely on the trees to photosynthesize; they use some of the tree’s chemical food as their only energy source. Such intimate relationships are examples of coevolution through which two species become so interdependent that they can thrive only in each other’s presence.
Question: According to the paragraph, what is the importance of mycorrhizal fungi to the trees?
A. They are an essential part of the tree’s mineral absorption process.
B. They provide energy to the tree through photosynthesis.
C. They allow the tree to produce seeds more rapidly.
D. They protect trees from pests and diseases.
Correct Answer: A
Explanation: The paragraph explains that these fungi facilitate mineral uptake from the soil, making them a vital component of the tree’s nutrition system. The defining relative clause “fungi that are indispensable to the tree” emphasizes that only these fungi are crucial for this process. Option A reflects this subtlety without overstating their role.
Option B is incorrect because the fungi do not provide energy through photosynthesis. Option C is wrong because seed production is not mentioned as part of their role. Option D is irrelevant, as protecting the tree from pests or disease is not discussed in this context.
Question 3
The following example is designed for TOEFL Reading Practice Test #41 – The Formation and Distribution of Petroleum.
Reading Passage: In the ocean, microscopic phytoplankton (tiny floating plants) and bacteria (simple, single-celled organisms) are the principal sources of organic matter that is trapped and buried in sediment. Most of the organic matter is buried in clay that is slowly converted to a fine-grained sedimentary rock known as shale. During this conversion, organic compounds are transformed into oil and natural gas, and additional chemical changes may occur in the oil and gas even after they have formed.
Question (Relative Clause): According to the paragraph, what happens to the organic matter that is trapped and buried in sediment?
A. It is immediately converted to oil.
B. It floats freely in the ocean for millions of years.
C. It is slowly buried in clay and transformed into shale.
D. It is ultimately transformed into oil and natural gas.
Correct Answer: D
Explanation: The paragraph contains two relative clauses: “that is trapped and buried in sediment” modifies organic matter, specifying which matter is being discussed. “That is slowly converted to a fine-grained sedimentary rock known as shale” modifies clay, describing the process it undergoes. Understanding the first clause allows students to identify the organic matter in question and trace its fate. The final outcome, after burial, conversion, and chemical transformation, is that the organic compounds are ultimately transformed into oil and natural gas. Option D correctly captures this complete process, while options A, B, and C either misrepresent the timing, oversimplify, or describe intermediate stages rather than the final result.
Examples from the IELTS Test
Question 1
This question is designed for Cambridge IELTS 20, Test 2, Reading module, Passage 3.
Reading Passage: Major League Baseball (MLB), who had commissioned the system, wanted human umpires to announce the calls, just as they would have done in the past. When the first pitch came in, a recorded voice told DeJesus it was a strike. Previously, calling a strike was a judgment call on the part of the umpire. Even if the batter does not hit the ball, a pitch that passes through the ‘strike zone’ (an imaginary zone about seventeen inches wide, stretching from the batter’s knees to the middle of his chest) is considered a strike. During that first game, when DeJesus announced calls, there was no heckling and no shouted disagreement. Nobody said a word.
Question: According to the paragraph, what does the clause “who had commissioned the system” tell us about MLB?
A. MLB was responsible for creating the robo-umpire system.
B. MLB opposed the use of robo-umpires.
C. MLB built the system themselves.
D. MLB refused to announce calls during the game.
Correct Answer: A
Explanation: The relative clause “who had commissioned the system” provides additional information about MLB, specifying that they authorized or arranged for the creation of the robo-umpire system. Understanding the clause allows students to correctly identify MLB’s role, distinguishing between the organization and the system itself, rather than confusing it with other details in the paragraph.
Question 2
This question is also designed for Cambridge IELTS 20, Test 2, Reading module, Passage 3.
Reading Passage: During the first robo-umpire season, players who were fed up with some strange calls decided to voice their concerns to MLB. In response, MLB adjusted the dimensions of the strike zone, and the following year the consensus was that the ABS system was far more consistent. MLB described the device as near-perfect, precise to within fractions of an inch. “It’ll reduce controversy in the game, and be good for the game,” said Rob Manfred, who is Commissioner for MLB.
Question: According to the paragraph, how did some players respond to the use of robo-umpires?
A. They were satisfied with the performance of the robo-umpire.
B. They became frustrated by the unusual calls.
C. They created the ABS system themselves.
D. They were professional coaches rather than players.
Correct Answer: B
Explanation: The relative clause “who were fed up with some strange calls” provides crucial information about the players’ reaction to the ABS system. Recognizing this clause helps students infer that the players’ dissatisfaction motivated their actions, distinguishing between those who accepted the system and those who voiced concerns. Option B correctly captures this nuance, while the other options are inconsistent with the paragraph.
Examples from the OET Test
Question 1
This question is designed for OET Official Practice Test 1 (Medicine), Reading Part C.
Reading Passage: A longitudinal study followed children who had sub-threshold ADHD in their youth, monitoring their development into adulthood. Patients who had sub-threshold ADHD in their youth were those who displayed mild symptoms that did not meet the full diagnostic criteria at the time. Interestingly, some of these patients developed full ADHD symptoms later in life, especially when environmental support was inconsistent. The researchers concluded that early identification and intervention, even in mild cases, can prevent progression to full-blown ADHD.
Question: Who were the patients described in the study?
A. Patients diagnosed with ADHD in childhood.
B. Patients who had mild ADHD symptoms in childhood but did not meet full criteria.
C. Patients with no ADHD symptoms in childhood.
D. Patients who received no early intervention.
Correct Answer: B
Explanation: The defining relative clause “who had sub-threshold ADHD in their youth” specifies the particular group of children being discussed—those with mild symptoms below diagnostic thresholds. Option B accurately identifies this group, while the other options either overstate the diagnosis or ignore the criteria described.
Test Your English Grammar Knowledge: Relative Clauses (Quiz)
Other Grammar Lessons
Watch a few of my videos to see how I approach teaching and what you can expect.
Ready to Start Your English IELTS TOEFL SAT Journey?
TAKE IT TO THE NEXT LEVEL.