Relative clauses are specialized components of English grammar that function as adjectives to provide essential or additional information about a noun or pronoun. These clauses allow speakers and writers to combine two separate thoughts into a single, sophisticated sentence, such as the man who lives next door, the book that I bought yesterday, the city where I was born, or the reason why she left early. By using these structures, you can avoid repetitive language and create a more fluid narrative style that connects ideas logically and efficiently. Understanding how to navigate relative pronouns and adverbs is a fundamental step for any English learner aiming to transition from basic sentence structures to academic or professional fluency.
Table of Contents
- 1. Comprehensive Definition of Relative Clauses
- 2. Structural Breakdown and Components
- 3. Understanding Relative Pronouns
- 4. Understanding Relative Adverbs
- 5. Defining (Restrictive) Relative Clauses
- 6. Non-Defining (Non-Restrictive) Relative Clauses
- 7. Extensive Examples and Reference Tables
- 8. Comprehensive Usage Rules and Punctuation
- 9. Common Mistakes and How to Avoid Them
- 10. Advanced Topics: Reducing Relative Clauses
- 11. Practice Exercises with Answer Key
- 12. Frequently Asked Questions (FAQ)
- 13. Conclusion and Final Tips
1. Comprehensive Definition of Relative Clauses
A relative clause is a type of subordinate clause (a dependent clause) that modifies a noun or a noun phrase. In the world of linguistics, these are often referred to as “adjective clauses” because they perform the exact same function as an adjective: they describe or identify a noun. Without the noun they are modifying, the relative clause cannot stand alone as a complete sentence.
The primary function of a relative clause is to provide more detail about a person, place, thing, or idea without starting a new sentence. For example, instead of saying “I met a woman. She works for NASA,” we can say “I met a woman who works for NASA.” Here, the bolded part is the relative clause. It tells us specifically which woman we are talking about.
Relative clauses are introduced by either a relative pronoun (who, whom, whose, which, that) or a relative adverb (where, when, why). The choice of which word to use depends entirely on what the noun is (person vs. thing) and what role that noun plays within the relative clause itself. Mastery of these clauses is essential for achieving “cohesion” in writing, which is the grammatical glue that holds complex ideas together.
2. Structural Breakdown and Components
To understand the anatomy of a relative clause, we must look at three specific parts: the antecedent, the relative word, and the rest of the clause. The antecedent is the noun or pronoun that comes before the clause and is being described. The relative word connects the clause to that antecedent.
The internal structure of the clause usually follows a Subject-Verb-Object (SVO) pattern, though the relative pronoun itself often acts as the subject or the object. For instance, in the sentence “The cake that Mary baked was delicious,” “cake” is the antecedent, “that” is the relative pronoun acting as the object of the verb “baked,” and “Mary” is the subject of the clause.
Another key structural element is the placement of the clause. A relative clause must always follow the noun it modifies as closely as possible. If the clause is placed too far from its antecedent, it creates a “misplaced modifier,” which can lead to confusion or unintended humor, such as “We sold the car to a man with a broken engine.” Placing the relative clause correctly—”We sold the car that had a broken engine to a man”—clarifies the meaning immediately.
3. Understanding Relative Pronouns
Relative pronouns are the most common way to start these clauses. Each pronoun has a specific job based on whether it refers to people, animals, or inanimate objects, and whether it represents the subject, object, or possessor in the clause.
Who is used for people when the person is the subject of the verb in the relative clause. Whom is used for people when the person is the object of the verb or follows a preposition. However, in modern spoken English, “who” is frequently used in place of “whom,” though formal writing still requires the distinction. Whose is the possessive form, used for both people and things to show ownership.
Which is reserved for animals and things. It is never used for people. That is a versatile pronoun that can be used for people, animals, or things, but it is primarily used in “defining” clauses. In many cases, “that” is preferred over “which” in American English for restrictive contexts, while “which” is mandatory for non-defining information.
4. Understanding Relative Adverbs
While relative pronouns act like nouns within a clause, relative adverbs function like adverbs, providing information about place, time, or reason. These adverbs replace a preposition plus a relative pronoun (like “in which” or “at which”) to make the sentence sound more natural.
Where is used to modify nouns referring to places. Instead of saying “The house in which I live,” we say “The house where I live.” When is used for nouns referring to time, such as “The day when we met.” Finally, Why is used almost exclusively after the noun “reason,” as in “The reason why he called is unknown.”
Using relative adverbs simplifies the sentence structure by removing the need for prepositions at the end of the clause. For example, “The hotel where we stayed” is often more elegant than “The hotel which we stayed at.” Both are grammatically correct, but the relative adverb offers a smoother transition between ideas.
5. Defining (Restrictive) Relative Clauses
A defining relative clause (also known as a restrictive clause) gives essential information about the noun. If you remove this clause, the sentence loses its primary meaning or becomes too vague to understand. For example, in the sentence “The students who studied hard passed the exam,” the clause “who studied hard” defines which specific students passed. If we remove it, “The students passed the exam” suggests all students passed, which changes the meaning.
Defining clauses are never set off by commas. This lack of punctuation signals to the reader that the information is vital to identifying the noun. In these clauses, the relative pronoun “that” is very common, and in certain circumstances, the relative pronoun can even be omitted entirely if it is the object of the clause (e.g., “The movie [that] I saw was great”).
These clauses are the workhorses of the English language, allowing us to narrow down broad categories into specific entities. They help us distinguish “the red car” from “the car that has a flat tire.” Without defining clauses, our ability to specify and clarify would be severely limited.
6. Non-Defining (Non-Restrictive) Relative Clauses
Non-defining relative clauses provide extra, non-essential information. The sentence would still make perfect sense and the noun would still be identifiable without the clause. For example: “My brother, who lives in New York, is a doctor.” Since I only have one brother (or the context makes it clear which one), the fact that he lives in New York is just an interesting detail, not a defining characteristic used to identify him.
In written English, non-defining clauses must be separated from the rest of the sentence by commas. If the clause is in the middle of the sentence, it needs a comma before and after it. If it is at the end, it needs a comma before it and a period after it. This punctuation acts like parentheses, indicating that the information is supplementary.
Crucially, you cannot use the pronoun “that” in a non-defining clause; you must use “who” for people and “which” for things. Additionally, you can never omit the relative pronoun in a non-defining clause, even if it serves as the object of the verb. These rules make non-defining clauses slightly more rigid in their structure than their defining counterparts.
7. Extensive Examples and Reference Tables
In this section, we provide detailed tables to illustrate how different relative pronouns and adverbs function across various contexts. These examples are designed to show the versatility of relative clauses in both formal and informal English.
Table 1: Relative Pronouns as Subjects
This table demonstrates sentences where the relative pronoun acts as the subject of the verb within the clause. In these cases, the pronoun cannot be omitted.
| Antecedent Type | Relative Pronoun | Example Sentence | Explanation |
|---|---|---|---|
| Person | who | The woman who won the lottery is my aunt. | “Who” is the subject of “won.” |
| Person | that | The man that shouted at us was very angry. | “That” is an informal alternative to “who.” |
| Thing | which | The car which is parked outside is mine. | “Which” is the subject of “is parked.” |
| Thing | that | The computer that crashed yesterday is fixed. | “That” is the subject of “crashed.” |
| Animal | who/that | The dog who barks at night belongs to Tom. | Pets are often referred to with “who.” |
| Person | who | Anyone who wants to join must sign up. | General subject reference. |
| Thing | which | The report which details the findings is long. | Formal subject reference. |
| Group | which | The team which wins the game gets a trophy. | Collective noun as antecedent. |
| Person | who | The doctor who treated me was very kind. | Identifying a specific person. |
| Thing | that | The tree that fell blocked the road. | Essential defining information. |
| Person | who | The artist who painted this is famous. | Subject of the action “painted.” |
| Thing | which | This letter, which arrived today, is for you. | Non-defining subject. |
| Person | who | The children who play here are noisy. | Plural subject. |
| Thing | that | The phone that is on the table is ringing. | Locating an object. |
| Person | who | The pilot who flew the plane was brave. | Defining the professional. |
| Thing | which | The book which inspired me is on the shelf. | Formal thing reference. |
| Animal | that | The cat that lives next door is black. | Defining the animal. |
| Person | who | Those who arrive late will not be admitted. | Generic plural subject. |
| Thing | that | The law that was passed is controversial. | Abstract noun as antecedent. |
| Person | who | The neighbor who helps me is very nice. | Subject of “helps.” |
Table 2: Relative Pronouns as Objects
This table shows instances where the relative pronoun is the object of the verb. In defining clauses, these pronouns can often be deleted (indicated by brackets).
| Antecedent Type | Relative Pronoun | Example Sentence | Object of… |
|---|---|---|---|
| Person | whom / [who] | The girl whom I met is a scientist. | Object of “met.” |
| Thing | [which / that] | The movie that we watched was boring. | Object of “watched.” |
| Person | [that] | The teacher that I like most is Mr. Smith. | Object of “like.” |
| Thing | [which] | The gift which you gave me is beautiful. | Object of “gave.” |
| Person | whom | The candidate whom they hired is skilled. | Formal object. |
| Thing | [that] | The dress that she wore was expensive. | Object of “wore.” |
| Person | [who] | The man who I saw yesterday was tall. | Informal object. |
| Thing | [which] | The cake which I baked is in the kitchen. | Object of “baked.” |
| Place | [that] | The city that I visited was crowded. | Object of “visited.” |
| Person | whom | To whom it may concern. | Object of preposition “to.” |
| Thing | [that] | The song that you are hearing is jazz. | Object of “hearing.” |
| Person | [that] | The boy that you saw is my cousin. | Object of “saw.” |
| Thing | [which] | The bike which he bought is fast. | Object of “bought.” |
| Person | whom | The author whom I admire is here. | Formal object. |
| Thing | [that] | The car that we rented was small. | Object of “rented.” |
| Person | [who] | The friend who I called didn’t answer. | Informal object. |
| Thing | [which] | The message which she sent was brief. | Object of “sent.” |
| Person | whom | The man for whom I work is strict. | Object of preposition “for.” |
| Thing | [that] | The house that they built is modern. | Object of “built.” |
| Person | [that] | The doctor that I consulted was helpful. | Object of “consulted.” |
Table 3: Usage of “Whose” and Relative Adverbs
The following table focuses on possession (whose) and the adverbs of place, time, and reason (where, when, why).
| Relative Word | Function | Example Sentence | Meaning |
|---|---|---|---|
| whose | Possession (People) | The boy whose dog died is very sad. | The dog of the boy. |
| whose | Possession (Things) | The house whose roof is red is mine. | The roof of the house. |
| where | Place | This is the park where we played. | In that park. |
| when | Time | I remember the day when we first met. | On that day. |
| why | Reason | I don’t know the reason why she left. | The reason for leaving. |
| whose | Possession | The singer whose voice is unique is on TV. | The voice of the singer. |
| where | Place | The office where I work is very far. | In that office. |
| when | Time | Summer is the time when it is hot. | During that time. |
| why | Reason | That is the reason why I am late. | The cause of being late. |
| whose | Possession | The mountain whose peak is snowy is tall. | The peak of the mountain. |
| where | Place | The restaurant where we ate was great. | At that restaurant. |
| when | Time | 1999 was the year when I graduated. | In that year. |
| whose | Possession | The student whose grades are high is Sam. | The grades of the student. |
| where | Place | The library where I study is quiet. | In that library. |
| when | Time | Evening is the time when I relax. | At that time. |
| why | Reason | Tell me the reason why you lied. | The motive for lying. |
| whose | Possession | The tree whose leaves fell is an oak. | The leaves of the tree. |
| where | Place | The town where I grew up is small. | In that town. |
| when | Time | The moment when she arrived was tense. | At that moment. |
| whose | Possession | The company whose CEO resigned is failing. | The CEO of the company. |
8. Comprehensive Usage Rules and Punctuation
Mastering relative clauses requires a deep understanding of several specific rules, particularly regarding punctuation and pronoun choice. One of the most critical rules concerns the use of commas. In a defining clause, commas are strictly forbidden because the clause is essential to identifying the noun. If you add commas, you change the logic of the sentence. For example, “The cars which have faulty brakes should be recalled” means only the dangerous cars need recalling. “The cars, which have faulty brakes, should be recalled” implies that all cars in the context have faulty brakes and should be recalled.
Another rule involves the omission of the relative pronoun. You can only omit the pronoun (who, whom, which, that) if it is the object of the relative clause. If the pronoun is the subject of the clause, it must remain. For example, in “The man [that] I saw,” “that” is the object of “saw,” so it can be removed. In “The man who saw me,” “who” is the subject of “saw,” so it cannot be removed. Note that “whose,” “where,” and “when” are rarely omitted, although “when” is sometimes dropped in informal speech after nouns like “day” or “time.”
Prepositions also play a major role in relative clause structure. In formal English, a preposition often comes before the relative pronoun (e.g., “The chair on which I sat”). In informal or spoken English, the preposition usually moves to the end of the clause (e.g., “The chair which I sat on“). If you move the preposition to the end, you can use “that” or even omit the pronoun entirely: “The chair I sat on.” However, if the preposition stays at the beginning, you must use “whom” for people or “which” for things; you cannot use “that.”
9. Common Mistakes and How to Avoid Them
One of the most frequent errors made by English learners is doubling the subject or object. Because the relative pronoun already represents the noun, you should not repeat the noun or a personal pronoun within the clause. For example, “The man who he lives here is my friend” is incorrect. The “he” is redundant because “who” already serves as the subject. The correct version is “The man who lives here is my friend.” Similarly, “The book that I bought it is good” is wrong; it should be “The book that I bought is good.”
Another common mistake is the misuse of “that” in non-defining clauses. Remember that “that” is strictly for defining information. If you have commas, you must use “which” or “who.” For instance, “My car, that is ten years old, still runs well” is grammatically incorrect. It should be “My car, which is ten years old, still runs well.” This is a rule that even native speakers sometimes struggle with in casual writing, but it is a hallmark of high-quality English prose.
Finally, learners often confuse “who” and “whose.” “Who” is a subject pronoun, while “whose” is a possessive adjective. If you are describing a person’s property or relationship, always use “whose.” Incorrect: “The woman who daughter is a doctor.” Correct: “The woman whose daughter is a doctor.” Checking whether you are describing an action (who) or a possession (whose) will help you choose the right word every time.
| Incorrect Sentence | Correct Sentence | Error Type |
|---|---|---|
| The man who he called me is my boss. | The man who called me is my boss. | Redundant subject |
| The movie that I saw it was great. | The movie that I saw was great. | Redundant object |
| Paris, that I love, is beautiful. | Paris, which I love, is beautiful. | “That” in non-defining clause |
| The girl which lives next door is nice. | The girl who lives next door is nice. | Wrong pronoun for person |
| The car who I bought is red. | The car that I bought is red. | Wrong pronoun for thing |
| The boy who’s bike was stolen cried. | The boy whose bike was stolen cried. | Who’s vs Whose confusion |
| The house where I live in is small. | The house where I live is small. | Redundant preposition with “where” |
| The reason because I’m late is traffic. | The reason why I’m late is traffic. | Wrong relative word |
| I met a man whom is a doctor. | I met a man who is a doctor. | Whom used as subject |
| The day which we met was sunny. | The day when we met was sunny. | Which vs When for time |
10. Advanced Topics: Reducing Relative Clauses
Advanced English speakers often “reduce” relative clauses to make their sentences more concise. A reduced relative clause turns the clause into a participial phrase. This is only possible when the relative pronoun is the subject of the clause. To reduce a clause with an active verb, you remove the relative pronoun and the “be” verb (if present) and change the main verb to its “-ing” form (present participle). For example, “The man who is standing there” becomes “The man standing there.”
To reduce a clause with a passive verb, you remove the relative pronoun and the “be” verb, leaving only the past participle. For example, “The report which was written by Sam” becomes “The report written by Sam.” This technique is extremely common in academic and journalistic writing because it allows for high information density without making the sentences feel cluttered or repetitive.
However, you cannot reduce a relative clause if the relative pronoun is the object of the clause. For instance, “The book that I read” cannot be reduced to “The book reading I” or “The book read I.” The reduction only works when the noun being modified is the one performing (active) or receiving (passive) the action described in the clause. Mastering this skill is a sign of advanced English proficiency.
11. Practice Exercises with Answer Key
Testing your knowledge is the best way to ensure you have grasped the nuances of relative clauses. Below are three sets of exercises ranging from basic identification to advanced sentence combining.
Exercise 1: Choose the Correct Relative Pronoun
Complete the following sentences by choosing the most appropriate relative pronoun (who, whom, whose, which, that).
- The woman ________ lives next door is a famous architect.
- The laptop ________ I bought last week is already broken.
- That is the man ________ wife won the marathon.
- The students ________ I teach are very hard-working.
- This is the house ________ my grandfather built.
- The scientist ________ discovered the cure was awarded a prize.
- The car, ________ cost a fortune, is now for sale.
- Do you know the girl ________ is talking to Tom?
- The books ________ are on the table belong to the library.
- The person to ________ you were speaking is my manager.
Exercise 2: Combine the Sentences
Combine the two sentences into one using a relative clause. Decide whether to use a defining or non-defining clause based on the context.
- I have a friend. He speaks five languages.
- The hotel was very expensive. We stayed there last summer.
- My mother is a great cook. She is 60 years old.
- The keys are on the counter. They belong to the blue car.
- The man was very friendly. I met him on the train.
- Rome is an ancient city. It is the capital of Italy.
- The children were playing outside. They got very muddy.
- The reason is unknown. He resigned so suddenly.
- The umbrella is in the hall. I borrowed it from you.
- A girl won the competition. Her father is a professional golfer.
Exercise 3: Answer Key
| Exercise 1 Answers | Exercise 2 Answers |
|---|---|
| 1. who / that | 1. I have a friend who speaks five languages. |
| 2. that / which | 2. The hotel where we stayed last summer was very expensive. |
| 3. whose | 3. My mother, who is 60 years old, is a great cook. |
| 4. whom / who / that | 4. The keys that are on the counter belong to the blue car. |
| 5. that / which | 5. The man whom I met on the train was very friendly. |
| 6. who | 6. Rome, which is the capital of Italy, is an ancient city. |
| 7. which | 7. The children who were playing outside got very muddy. |
| 8. who / that | 8. The reason why he resigned so suddenly is unknown. |
| 9. that / which | 9. The umbrella (that) I borrowed from you is in the hall. |
| 10. whom | 10. The girl whose father is a professional golfer won the competition. |
12. Frequently Asked Questions (FAQ)
Q1: Can I always use “that” instead of “who” or “which”?
A: Not always. You can use “that” instead of “who” or “which” only in defining clauses. In non-defining clauses (those with commas), you must use “who” for people and “which” for things. Also, in formal writing, “who” is preferred over “that” when referring to people.
Q2: When can I omit the relative pronoun?
A: You can omit the pronoun (who, whom, which, that) only when it is the object of the relative clause. For example, “The book [that] I read.” If it is the subject, like in “The man who called,” you cannot omit it.
Q3: What is the difference between “who” and “whom”?
A: “Who” is a subject pronoun (like “he” or “she”), meaning it performs the action. “Whom” is an object pronoun (like “him” or “her”), meaning it receives the action or follows a preposition. In modern casual English, “who” is often used for both, but “whom” remains necessary in formal contexts.
Q4: Do I need a comma before “which”?
A: You need a comma before “which” if the clause is non-defining (extra information). If the clause is defining (essential information), you do not use a comma. In American English, “that” is usually preferred for defining clauses to avoid this confusion.
Q5: Can “whose” be used for inanimate objects?
A: Yes! While “whose” is the possessive of “who,” it is perfectly acceptable and common to use it for things to avoid the clunky “of which” construction. For example, “The car whose alarm is ringing” is more natural than “The car the alarm of which is ringing.”
Q6: Is it wrong to end a relative clause with a preposition?
A: No, it is not wrong. While old-fashioned grammarians once argued against it, ending a sentence or clause with a preposition (e.g., “The man I was talking to“) is standard in modern English. Moving the preposition to the front (“The man to whom I was talking”) is very formal.
Q7: What is a “sentential” relative clause?
A: This is a special type of non-defining clause using “which” that refers back to the entire preceding sentence rather than just one noun. For example: “He passed his exams, which surprised everyone.” Here, “which” refers to the fact that he passed, not to the exams themselves.
Q8: How do I know if a clause is defining or non-defining?
A: Ask yourself: “If I remove this clause, do I still know exactly which person or thing is being talked about?” If the answer is no, it’s defining (no commas). If the answer is yes, it’s non-defining (use commas).
13. Conclusion and Final Tips
Relative clauses are a powerful tool in the English language, enabling you to provide detail, clarify identity, and connect complex thoughts with precision. Whether you are using a defining clause to specify exactly which book you are referring to, or a non-defining clause to add an interesting anecdote about a friend, these structures are vital for natural-sounding communication. Remember the key distinctions: use “who” for people, “which” for things, and “that” only in defining contexts. Pay close attention to your commas, as they change the very logic of your sentences. To master this topic, practice combining short, choppy sentences into longer, more elegant ones. With consistent application of these rules, your writing will become more fluid, professional, and engaging for any reader.
