Relative clauses: who, which, that and commas (grammar notes with exercises)

What you need to know

A relative clause gives more information about a noun. It usually comes straight after that noun and begins with a relative pronoun or a relative adverb. Relative clauses let you join two short sentences into one, which makes writing smoother and more mature. They are also one of the most common sources of error in CSS précis and composition papers and in O Level directed and continuous writing.

Relative pronouns and relative adverbs

Word	Refers to	Example
who	people (subject, and object in informal English)	The officer who signed the order has retired.
whom	people (object, or after a preposition; formal)	The candidate whom the panel selected was from Quetta.
whose	possession, for people, animals and things	The farmer whose crops failed applied for a loan.
which	animals and things; also a whole previous clause	The bridge which collapsed was only ten years old.
that	people, animals or things, in defining clauses only	This is the report that caused the debate.
where	places (= in which, at which)	Lahore is the city where I was born.
when	times (= on which, in which)	1947 was the year when Pakistan came into being.
why	reasons, after "the reason"	That is the reason why the project failed.

The relative pronoun replaces a noun or pronoun in the clause. Never repeat that noun with another pronoun: "the book which I bought it" is wrong.

Defining and non-defining clauses

Learn these two definitions

A defining (restrictive) relative clause identifies which person or thing we mean. The sentence loses its essential meaning without it. It takes no commas, and you may use who, which or that.

A non-defining (non-restrictive) relative clause adds extra information about a person or thing that is already identified. The sentence still makes complete sense without it. It is separated by commas (or a comma and a full stop), and you may not use that.

Compare:

• My brother who lives in Karachi is a doctor. (Defining: I have more than one brother, and I mean the one in Karachi.)
• My brother, who lives in Karachi, is a doctor. (Non-defining: I have one brother, and his home is extra information.)

Proper nouns, and nouns made unique by words such as "my mother" or "the Prime Minister of Pakistan", are already identified, so a clause after them is normally non-defining: "Allama Iqbal, who was born in Sialkot, is known as the poet of the East."

A non-defining clause in the middle of a sentence needs two commas, one at each end. A very common error is to open the clause with a comma and forget to close it.

Whom and whose

Use whom when the pronoun is the object of the verb in the clause, or straight after a preposition. A quick test: if you could answer with "him" or "them", whom is correct; if you could answer with "he" or "they", use who. In everyday English "who" often replaces object "whom", but in CSS papers, formal letters and essays "whom" is expected.

Whose shows possession and is always followed by a noun: "the student whose essay won". Do not confuse it with who's, which means "who is" or "who has". Whose may refer to things: "a country whose economy depends on agriculture".

Omitting the relative pronoun

In a defining clause you may leave out who, whom, which or that when it is the object of the clause:

• The book (that) I borrowed was out of print. (I borrowed the book: object, so it can go.)
• The book that won the prize was out of print. (The book won: subject, so it must stay.)

You can never leave out the pronoun in a non-defining clause, and you cannot leave out whose.

Prepositions with relative pronouns

A preposition can come at the start of the clause (formal) or at the end (informal):

• Formal: The committee to which the matter was referred has not met.
• Informal: The committee (which / that) the matter was referred to has not met.

After a preposition use only whom (people) or which (things). "With who" and "in that" are wrong. Quantity phrases also use whom and which in non-defining clauses: "The villagers, many of whom had lost their homes, waited for aid." "He gave three reasons, none of which convinced the board."

Which referring to a whole clause

A non-defining clause with which can comment on the whole of the previous idea: "The train was four hours late, which annoyed the passengers." Here "that" or "what" cannot be used.

Reduced relative clauses

A relative clause can often be shortened to a participle phrase:

• Active, -ing: People who live near the river are at risk → People living near the river are at risk.
• Passive, -ed: The goods which were seized at the port were destroyed → The goods seized at the port were destroyed.
• To-infinitive after first, last, only, or a superlative: She was the first woman who reached the summit → She was the first woman to reach the summit.

Reduced clauses are useful in précis, where you must save words without losing meaning.

Worked example

Join these sentences with a relative clause: "Quaid-e-Azam addressed the Constituent Assembly on 11 August 1947. He was its first President."

Step 1: the shared person is Quaid-e-Azam, a proper noun, so the clause is non-defining and needs commas.

Step 2: "He" is the subject, so use who.

Answer: Quaid-e-Azam, who was the first President of the Constituent Assembly, addressed it on 11 August 1947.

Exam tip: common errors in CSS and O Level writing

• Using which for people: "the officers which" → "the officers who".
• Using that in a non-defining clause: "Islamabad, that is the capital" → "Islamabad, which is the capital".
• Adding an extra pronoun: "the policy which the government announced it" → delete "it".
• Using what as a relative pronoun: "the thing what I need" → "the thing that I need" or "what I need".
• Writing who's for whose, or putting a comma before a defining clause.
• Leaving a relative clause without a main verb: "The students who passed the test." This is a fragment, not a sentence.

Questions

Section A: choose the correct word (1 to 8)

Complete each sentence with who, whom, whose, which, where or when.

1. The engineer ______ designed the dam received an award.
2. Murree is a hill station ______ many families spend the summer.
3. I met a writer ______ novels have been translated into Urdu.
4. The laptop ______ I bought last week has stopped working.
5. Do you remember the day ______ the results were announced?
6. The minister, ______ the journalists criticised, refused to resign.
7. The Indus, ______ rises in Tibet, flows into the Arabian Sea.
8. To ______ should I address this complaint?

Section B: defining or non-defining? Add commas where needed (9 to 14)

State whether each relative clause is defining or non-defining, and rewrite the sentence with correct punctuation.

1. The students who arrived late missed the instructions.
2. Karachi which is Pakistan's largest city is a major port.
3. My father who is a retired teacher still reads every evening.
4. The medicine that the doctor prescribed made me sleepy.
5. Mount Everest which was first climbed in 1953 attracts hundreds of climbers each year.
6. Explain the difference in meaning between these two sentences: (a) The passengers who had tickets boarded the plane. (b) The passengers, who had tickets, boarded the plane.

Section C: join the sentences (15 to 19)

Join each pair using a relative clause. Use commas where necessary.

1. The woman is my aunt. She is standing by the door.
2. Faisal Mosque is in Islamabad. It was completed in 1986.
3. The scientist won the prize. Her research was on water purification.
4. The colleague is on leave. I usually share my office with him. (Write a formal version with a preposition before the pronoun.)
5. Fifty labourers were working on the site. Most of them were from Punjab.

Section D: can the pronoun be left out? (20 to 23)

Say whether the relative pronoun can be omitted. Give a reason.

1. The film that we watched was too long.
2. The film that won the award was too long.
3. My car, which I bought in 2020, needs new tyres.
4. The man whom you saw at the bank is my uncle.

Section E: correct the errors (24 to 27)

Each sentence contains one error with a relative clause. Rewrite it correctly and explain the error.

1. The officers which investigated the case were transferred.
2. The report that the committee submitted it was rejected.
3. Lahore, that is famous for its food, attracts many tourists.
4. The candidate who's application was late was not interviewed.

Section F: higher level (28 to 30)

1. Reduce the relative clause to a participle phrase: "The documents which were found in the archive changed our view of the period."
2. Reduce the relative clause using a to-infinitive: "Fatima Jinnah was the first woman who contested a presidential election in Pakistan."
3. Rewrite this extract from a student's précis in fewer words, using relative clauses or reduced clauses and correct punctuation: "Pakistan has many rivers. These rivers provide water for farming. Farming employs a large part of the workforce. However, the rivers are polluted by industry. This worries environmentalists."

Answers

Section A

1. who. It refers to a person and is the subject of "designed". (That is also correct here.)

2. where. It refers to a place and means "in which".

3. whose. It shows possession (the writer's novels) and is followed by the noun "novels".

4. which (or that, or no pronoun). It refers to a thing and is the object of "bought".

5. when. It refers to a time and means "on which".

6. whom. The minister is the object of "criticised" (the journalists criticised him), and the clause is non-defining, so that cannot be used. "Who" would be accepted in informal English but whom is the formal choice.

7. which. The Indus is a thing (a river) and the clause is non-defining, marked by commas.

8. whom. It comes straight after the preposition "to", so who is not correct.

Section B

9. Defining. Only the late students missed the instructions, so the clause identifies which students. No commas: The students who arrived late missed the instructions.

10. Non-defining. Karachi is a proper noun and is already identified. Karachi, which is Pakistan's largest city, is a major port.

11. Non-defining, because a person has only one father. My father, who is a retired teacher, still reads every evening.

12. Defining. It tells us which medicine. No commas: The medicine that the doctor prescribed made me sleepy.

13. Non-defining. Mount Everest, which was first climbed in 1953, attracts hundreds of climbers each year.

14. In (a) the clause is defining: only the passengers with tickets boarded, which suggests some passengers had no tickets and did not board. In (b) the clause is non-defining: all the passengers boarded, and all of them had tickets. The commas change the meaning, not just the style.

Section C

15. The woman who is standing by the door is my aunt. (Defining, no commas. "That" is also correct. A reduced version is "The woman standing by the door is my aunt.")

16. Faisal Mosque, which was completed in 1986, is in Islamabad. (Non-defining because it is a proper noun.)

17. The scientist whose research was on water purification won the prize. (Whose replaces "her" and shows possession.)

18. The colleague with whom I usually share my office is on leave. (Formal: preposition + whom. The informal version is "The colleague I usually share my office with is on leave.")

19. Fifty labourers, most of whom were from Punjab, were working on the site. (After "most of" use whom, not them or who.)

Section D

20. Yes. "That" is the object of "watched" (we watched the film) in a defining clause: The film we watched was too long.

21. No. "That" is the subject of "won" (the film won the award). Without it the sentence becomes ungrammatical.

22. No. The clause is non-defining (marked by commas), and the pronoun can never be omitted from a non-defining clause, even when it is the object.

23. Yes. "Whom" is the object of "saw" in a defining clause: The man you saw at the bank is my uncle.

Section E

24. The officers who investigated the case were transferred. Which is used for things, not people.

25. The report that the committee submitted was rejected. The relative pronoun "that" already stands for the report, so the extra object "it" must be removed.

26. Lahore, which is famous for its food, attracts many tourists. That cannot introduce a non-defining clause; after a proper noun with commas, use which.

27. The candidate whose application was late was not interviewed. Who's means "who is" or "who has"; possession needs whose.

Section F

28. The documents found in the archive changed our view of the period. The clause is passive ("were found"), so it is reduced to the past participle "found" by removing "which were".

29. Fatima Jinnah was the first woman to contest a presidential election in Pakistan. After "the first", a to-infinitive can replace "who contested".

30. A model answer: Pakistan's many rivers, which provide water for farming, a sector employing a large part of the workforce, are polluted by industry, which worries environmentalists. This reduces 28 words to 24. Points to note: "which provide water for farming" is non-defining, so it has commas; "employing a large part of the workforce" is a reduced clause; and the final "which" refers to the whole idea that the rivers are polluted, so it follows a comma. Other versions are acceptable if every original idea is kept, the punctuation is correct and no relative clause is left without a main verb.