Relative pronouns introduce relative clauses that give information about a person, thing, or idea. The five commonly taught relative pronouns in English are who, whom, whose, which, and that.
For example:
The engineer who inspected the bridge recommended further repairs.
Who refers to the engineer and introduces the clause who inspected the bridge. This clause identifies which engineer is being discussed.
Choosing the right relative pronoun depends on what it refers to, its function in the clause, and whether the information is necessary to identify someone or something.
Relative Pronouns List
The five common relative pronouns have different uses.
| Relative pronoun | Main use | Example |
|---|---|---|
| Who | Refers to people, commonly as a subject | The researcher who led the study answered our questions. |
| Whom | Refers to people as an object, especially in formal English | The consultant whom we hired has extensive experience. |
| Whose | Expresses a possessive relationship | The author whose manuscript was selected received an award. |
| Which | Refers mainly to things and animals | The equipment which arrived yesterday needs testing. |
| That | Refers to people, animals, or things in defining relative clauses | The documents that require signatures are on your desk. |
The uses are not completely separate.
For example, that can refer to people in defining relative clauses.
The technician that repaired the equipment has left for the day.
Whose can also express a relationship involving things rather than people.
The museum whose roof was damaged has reopened.
Traditional grammar commonly groups these five forms as relative pronouns. Some modern grammatical descriptions treat whose as a relative determiner when it comes before a noun and analyze that differently in certain clause constructions.
For ordinary grammar learning, the five-form list remains a useful starting point.
How Relative Pronouns Work in Sentences
A relative pronoun connects information in a relative clause to a person or thing mentioned elsewhere in the sentence.
Consider:
A designer presented the revised drawings.
The designer works for our company.
We can combine the statements:
The designer who works for our company presented the revised drawings.
The clause who works for our company identifies the designer.
Within that clause, who functions as the subject of works.
Now compare:
The designer whom we consulted presented the revised drawings.
Here, whom refers to the designer, but it represents the object of consulted. The subject of that verb is we.
This subject–object distinction helps explain why different relative forms are used and why some can be omitted.
Who vs. Whom
Who is the usual form when referring to a person who functions as the subject of a relative clause.
The scientist who discovered the error contacted the laboratory.
The scientist performed the action of discovering.
Whom is an object form, used mainly in formal English.
The scientist whom the committee interviewed has accepted the position.
The committee performed the interview. The scientist was the person interviewed.
In everyday English, who is also widely used in object positions.
The scientist who the committee interviewed has accepted the position.
Both forms are grammatical. Whom sounds more formal, while who is common in conversation and contemporary writing.
How to Choose Between Who and Whom
A useful approach is to identify the subject of the verb inside the relative clause.
Compare:
The editor who approved the manuscript is away.
The editor approved the manuscript, so who functions as the subject.
The editor whom we consulted is away.
We consulted the editor, so whom represents the object.
You can often check the distinction by turning the relative clause into a separate sentence.
She approved the manuscript corresponds to subject who.
We consulted her corresponds to object whom in formal usage.
The distinction is grammatical, but modern usage allows who in many positions where traditional formal grammar uses whom.
Whom After Prepositions
Whom is particularly common when a preposition appears immediately before the relative pronoun.
The manager to whom I sent the documents replied this morning.
In everyday English, the preposition often appears later.
The manager who I sent the documents to replied this morning.
The relative pronoun can also be omitted:
The manager I sent the documents to replied this morning.
These versions communicate the same basic relationship, but their formality differs.
Which vs. That: Choosing the Right Form
Which and that can both refer to things and animals in defining relative clauses.
A defining relative clause identifies or restricts the person or thing being discussed.
Compare:
The files which contain confidential information require encryption.
The files that contain confidential information require encryption.
Both sentences identify the files that need encryption.
In American edited English, many style guides prefer that in defining clauses and which in non-defining clauses.
British English commonly uses which in defining clauses as well.
Neither sentence above is grammatically incorrect.
When Commas Change the Meaning
A non-defining relative clause adds information about someone or something already identifiable. It is separated by commas and normally uses who, whom, whose, or which, rather than that.
Compare:
The employees who completed the safety training may operate the equipment.
The employees, who completed the safety training, may operate the equipment.
In the first sentence, the relative clause identifies which employees may operate the equipment.
In the second, the employees are treated as an already identified group. The clause adds the information that they completed the training.
The commas change how the reader understands the group.
Another example:
My sister who lives in Edinburgh is visiting tomorrow.
My sister, who lives in Edinburgh, is visiting tomorrow.
In the first sentence, the relative clause identifies which sister is meant. It may suggest that the speaker has more than one sister.
In the second, the sister is already identifiable, and her place of residence is additional information.
Neither sentence proves how many sisters the speaker has. Context still matters.
Why That Cannot Replace Which in Every Sentence
That is used in defining relative clauses, not standard non-defining ones.
Incorrect:
The revised contract, that arrived this morning, needs approval.
Correct:
The revised contract, which arrived this morning, needs approval.
The clause is presented as additional information, so which is appropriate.
A defining version is also grammatical:
The revised contract that arrived this morning needs approval.
Here, the arrival information identifies the contract.
When Which Refers to an Entire Clause
Which can refer not only to a noun but also to an entire preceding statement or situation.
Compare:
The inspection, which was scheduled for Monday, has been postponed.
Here, which refers to the inspection.
Now consider:
The council postponed the inspection, which frustrated the residents.
In this sentence, which refers to the fact that the inspection was postponed.
The residents were frustrated by the postponement, rather than necessarily by the inspection itself.
When a non-defining relative clause comments on an entire preceding statement, which is the usual form. That cannot replace it in this construction.
When Can You Omit a Relative Pronoun?
A relative pronoun can sometimes be omitted from a defining relative clause when it represents an object.
Compare:
The documentary that we watched last night was fascinating.
The documentary we watched last night was fascinating.
Both sentences are grammatical.
In the first, that represents the object of watched. In the second, that object relationship is understood without an expressed relative pronoun.
When the Pronoun Is the Subject
A subject relative pronoun normally cannot be omitted from an ordinary finite relative clause.
Correct:
The mechanic who repaired the engine explained the problem.
Incorrect:
The mechanic repaired the engine explained the problem.
In the correct sentence, who is the subject of repaired.
Removing it leaves the intended relative clause without the required subject.
In Non-Defining Relative Clauses
The relative pronoun cannot normally be omitted.
Correct:
The documentary, which we watched last night, was fascinating.
Incorrect:
The documentary, we watched last night, was fascinating.
The relative clause adds non-defining information, so which must remain.
After Prepositions
When a relative pronoun represents the object of a preposition, it may be omitted in a defining clause if the preposition remains later in the clause.
The software that we relied on has been replaced.
The software we relied on has been replaced.
Both are correct.
A more formal version places the preposition before which:
The software on which we relied has been replaced.
But the relative pronoun cannot be omitted while leaving the preposition in that position.
Incorrect:
The software on we relied has been replaced.
Similarly, that cannot immediately follow a fronted preposition in this construction.
Incorrect:
The software on that we relied has been replaced.
Use on which or place on later in the clause.
Whose and Possessive Relationships
Whose expresses a possessive relationship within a relative clause.
The architect whose drawings were approved will supervise the project.
The drawings are associated with the architect.
Whose can also refer to an organization, building, or other thing.
The building whose entrance was damaged remains closed.
Here, whose entrance identifies the entrance forming part of the building.
When whose appears before a noun, as in whose drawings or whose entrance, it functions as a possessive relative determiner in modern grammatical descriptions.
Whose vs. Who’s
Whose is possessive.
The student whose project won the competition received a certificate.
Who’s is a contraction of who is or who has.
Who’s presenting the results tomorrow?
The two forms sound alike but have different grammatical functions.
Can What Be a Relative Pronoun?
English also uses what in constructions where it means approximately the thing that or the things that.
What you suggested makes sense.
This has a similar meaning to:
The thing that you suggested makes sense.
The expression what you suggested is often called a free relative clause or fused relative clause. It does not require a separate noun before what.
Compare:
Correct:
The suggestion that you made makes sense.
Incorrect in standard English:
The suggestion what you made makes sense.
When the noun suggestion is already present, use that or which in this construction.
Other forms, including whoever and whatever, can introduce similar free relative constructions.
Whoever finishes the inspection first should submit the report.
You may choose whatever suits your requirements.
These constructions have their own grammatical patterns. They do not make what an interchangeable alternative to all five commonly taught relative pronouns.
Relative Pronouns vs. Relative Adverbs
Words such as where, when, and why can introduce relative clauses, but they are traditionally called relative adverbs rather than relative pronouns.
They commonly express relationships involving place, time, or reason.
Compare:
This is the town where we stayed during the conference.
This is the town that we visited during the conference.
In the first sentence, where identifies the place in which the staying occurred.
In the second, that represents the town as the object of visited.
The preceding noun does not automatically determine which relative form is needed.
A similar distinction applies to time.
I remember the day when the results were announced.
I remember the day that changed our plans.
When introduces a time relationship.
That refers to the day as the subject of changed.
The intended relationship within the relative clause determines which form makes sense.
How to Choose and Correct Relative Pronouns in Context
Choosing a relative pronoun involves more than checking whether the preceding noun refers to a person or thing.
Consider these three sentences:
The coordinator who reviewed the proposal is on leave.
The coordinator whom we consulted is on leave.
The coordinator whose proposal was approved is on leave.
Each refers to a coordinator, but the relative forms perform different functions.
| Relative expression | Function | Meaning |
|---|---|---|
| who reviewed the proposal | Subject | The coordinator performed the review |
| whom we consulted | Object | We consulted the coordinator |
| whose proposal was approved | Possessive relationship | The proposal is associated with the coordinator |
Once the grammatical role is clear, the next step is to check whether the sentence communicates the intended meaning without unnecessary words or unclear references.
Avoid Repeating an Object
Incorrect:
The computer that we repaired it is working again.
Correct:
The computer that we repaired is working again.
That already represents the computer as the object of repaired. Adding it repeats the same object in the intended relative-clause construction.
The relative pronoun can also be omitted:
The computer we repaired is working again.
Avoid Repeating a Subject
Incorrect:
The technician who she repaired the computer is on leave.
Correct:
The technician who repaired the computer is on leave.
In the correct sentence, who is the subject of repaired. An additional she is not needed.
If another woman performed the relevant action, the sentence needs a different structure.
The technician whom she consulted is on leave.
Now she is the subject of consulted, while whom represents the person consulted.
Make the Reference Clear
Consider:
I met the assistant of the photographer who won the award.
Who won the award: the assistant or the photographer?
The relative clause who won the award could reasonably be understood as referring to either person.
If the photographer won:
I met the assistant of the photographer who had won the award.
Although this version makes the photographer the more natural reference, a clearer revision is:
I met an assistant who works for the award-winning photographer.
If the assistant won:
I met the photographer’s assistant. The assistant had recently won the award.
The best revision depends on the intended meaning. Sometimes a relative clause can be clarified by moving it. In other cases, using a second sentence is more effective.
A Practical Way to Check Your Sentence
When choosing a relative pronoun, identify the person, thing, or statement that the relative clause refers to.
Then check whether the pronoun functions as a subject, an object, or part of a possessive expression.
Next, decide whether the relative clause identifies something or adds information about something already identifiable. This affects punctuation and whether that can be used.
Finally, check for an unnecessary repeated pronoun or a relative clause that could refer to the wrong noun.
The aim is not simply to produce a grammatical sentence. It is to make the intended meaning clear.
Check Your Understanding
Choose the correct form, decide whether omission is possible, or revise the sentence.
1. Choose the correct relative pronoun.
The engineer (who / which) inspected the tunnel identified several defects.
2. Choose the correct form for formal writing.
The representative to (who / whom) we addressed the complaint responded promptly.
3. Can the relative pronoun be omitted?
The documentary that the students recommended is available online.
4. Correct the repeated object.
The laptop that the technician repaired it is working properly.
5. Identify what which refers to.
The organizers cancelled the outdoor concert, which disappointed many visitors.
Does which refer to the concert itself or to the cancellation?
6. Choose the correct relative expression.
I appreciated (what / which) you suggested during the meeting.
7. Explain the difference in meaning.
The applicants who passed the interview received an offer.
The applicants, who passed the interview, received an offer.
Answers
1. Who
Who refers to the engineer and functions as the subject of inspected.
2. Whom
Whom is the formal object form used after the preposition to.
The correct sentence is:
The representative to whom we addressed the complaint responded promptly.
3. Yes
That represents the object of recommended in a defining relative clause.
The sentence can be written as:
The documentary the students recommended is available online.
4. Remove it
The corrected sentence is:
The laptop that the technician repaired is working properly.
That already represents the laptop as the object of repaired.
5. The cancellation
Which refers to the preceding situation: the organizers cancelling the outdoor concert.
The visitors were disappointed by that decision.
6. What
The correct sentence is:
I appreciated what you suggested during the meeting.
What you suggested means approximately the thing that you suggested.
7. Defining vs. non-defining meaning
In the first sentence, the clause identifies which applicants received offers. It does not say that every applicant passed the interview.
In the second, the applicants are treated as an already identified group. The clause adds the information that they passed the interview.
The commas affect whether the clause identifies a subgroup or supplies additional information about the group.
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