Relative Clauses: Who, Which, That, and Where

A relative clause describes a noun. Use who or that for people, that or which for things, and where for places. Keep the relative word when it is the clause’s subject. In a defining clause, you may omit it when it is the object. Use commas around a nondefining clause that adds extra information.

That short rule handles many everyday sentences. The next step is deciding whether the description identifies the noun or simply adds a detail.

Relative clauses at a glance

Relative word	Common use	Example
who	People	“The neighbor who called left a message.”
that	People or things in defining clauses	“I found the key that opens the side door.”
which	Things; especially extra information	“The café, which opens at seven, is nearby.”
whose	Possession	“We met a designer whose work won an award.”
where	Places	“This is the room where we practice.”
when	Times	“Friday is the day when Sam works from home.”

Who, which, that, and whose are relative pronouns. Where and when are relative adverbs, but they do the same connecting job in the examples above.

Defining (restrictive) clauses identify the noun

A defining (restrictive) relative clause tells the listener which person or thing you mean. It is essential to the sentence’s intended meaning, so it does not take commas:

• “The customer who ordered the blue lamp is here.”
• “Please bring the form that needs a signature.”
• “The apartment which faces the park costs more.”

For a person, who often sounds most natural, but that is also standard in a defining clause: “The person that answered was helpful.” For a thing, both that and which can be grammatical. Many American style guides prefer that in defining clauses, especially in edited prose.

Nondefining (nonrestrictive) clauses add extra information

A nondefining (nonrestrictive) relative clause does not identify the noun. It adds information about a person or thing that is already clear. Put a comma before and after the clause when it appears in the middle of a sentence:

• “Mia, who works upstairs, will join us at noon.”
• “My phone, which is five years old, still works.”

Do not use that for this extra-information pattern. Use who for a person and which for a thing. Do not omit the relative pronoun.

Commas can change the meaning. Compare:

• “The employees who work remotely will meet online.” This identifies the employees who work remotely.
• “The employees, who work remotely, will meet online.” This presents remote work as extra information about all the employees already under discussion.

Keep the relative word when it is the subject

Find the verb inside the relative clause. If the relative word performs that action, it is the subject and must stay:

“We need a guide who knows the neighborhood.”

Who is the subject of knows. “We need a guide knows the neighborhood” is not standard English. The same rule applies to things: “I need a charger that works,” not “I need a charger works.”

An object relative pronoun may disappear

When that, which, who, or whom is the object of the verb in a defining clause, you may keep it or omit it:

• “The book that Ben recommended is available.”
• “The book Ben recommended is available.”

Ben is the subject of recommended; the book is its object. Both versions are correct. The same option applies to people:

• “The manager who Emma called replied.”
• “The manager that Emma called replied.”
• “The manager Emma called replied.”

Whom is also grammatically possible as the object: “The manager whom Emma called replied.” In everyday American conversation, speakers commonly use who, that, or no relative pronoun instead. After a fronted preposition, whom remains the careful form: “the person to whom I spoke.” The conversational version is usually “the person I spoke to.”

Use whose for possession

Whose connects a person or thing with something that belongs to it or is associated with it:

• “I spoke with the tenant whose package was missing.”
• “They chose a company whose office is near the station.”

Whose is not the same as who’s. Who’s is a contraction of who is or who has.

Use where for a place

Where means “in which” or “at which” in a place description:

• “That is the café where we first met.”
• “This is the desk where Sam keeps the receipts.”

You can often express the same idea with a preposition: “That is the café at which we first met.” In conversation, a defining clause with the preposition at the end is also natural: “That is the café we first met at.”

Do not use where when the place noun performs the action. Say “the road that leads downtown,” because the road is the subject of leads. “The road where leads downtown” is incorrect.

Use when for a time

When can introduce a clause after a time noun:

• “Monday is the day when the store closes early.”
• “I remember the year when Emma moved here.”

In a defining clause, when may sometimes be replaced by that or omitted: “I remember the year that Emma moved here” and “I remember the year Emma moved here.”

Shorten a clause only when the structure allows it

Some subject relative clauses can become participial phrases. A clause with a continuous form may lose the relative word and be:

• “The people who are waiting outside” becomes “the people waiting outside.”
• “The train that is arriving now” becomes “the train arriving now.”

A passive clause can often be shortened to a past-participle phrase:

• “The forms that were sent yesterday” becomes “the forms sent yesterday.”

Do not remove words mechanically. “The guide who knows the area” usually does not become “the guide knowing the area” in everyday English; with verbs such as know, own, and want, the -ing form sounds formal or awkward.

Use pauses to make extra information clear

In speech, a nondefining clause often forms its own small thought group, with a pause before and after it: “Mia | who works upstairs | will join us.” Ledoly’s guide to thought groups and pausing shows how these chunks help listeners follow a sentence.

In writing, commas do that boundary work. The guide to email English versus meeting English can help you choose a complete written form when a shorter spoken version might be unclear.

Practice: choose every natural answer

Complete each sentence. The answer key lists every standard natural form allowed by the prompt.

1. Use a defining clause about a person: “The doctor ___ called this morning left a message.”
2. Use a defining clause about a thing: “The bus ___ stops here goes downtown.”
3. Complete the object clause: “The movie ___ Sam recommended was funny.”
4. Add a nondefining clause with the needed punctuation and relative word: “My laptop ___ is four years old ___ needs a new battery.”
5. Show possession: “I met a musician ___ sister lives nearby.”
6. Describe a place with where: “This is the room ___ we record the lessons.”
7. Choose where, that, or which: “Take the road ___ leads to the park.”
8. Can you omit the relative word? “The neighbor who owns the red bike is away.”
9. Shorten the continuous relative clause: “The customers who are waiting outside have appointments.”
10. Shorten the passive relative clause: “The packages that were delivered today are on the table.”

Answer key

1. who or that — the relative word is the subject of called, so it cannot be omitted.
2. that or which — both are grammatical in this defining clause; many American style guides prefer that.
3. that, which, or no relative pronoun — Sam is the subject, so the movie is the object of recommended.
4. My laptop, which is four years old, needs a new battery. The clause adds extra information, so use which and two commas.
5. whose — the sister is associated with the musician.
6. where — “in which” is also grammatical, but the prompt asks for where.
7. that or which — the road performs the action, so where is incorrect.
8. No. Who is the subject of owns and must stay. That can replace who.
9. The customers waiting outside have appointments.
10. The packages delivered today are on the table.

Frequently asked questions

What is a relative clause?

A relative clause describes a noun. It commonly begins with a word such as who, which, that, whose, where, or when.

What is the difference between defining and nondefining relative clauses?

A defining (restrictive) clause identifies which person or thing you mean and does not take commas. A nondefining (nonrestrictive) clause adds extra information, uses commas, and does not begin with that.

When can I omit who, which, or that?

You may omit an object relative pronoun in a defining clause: “The book that Ben recommended” can become “the book Ben recommended.” Do not omit a subject relative pronoun or a pronoun in a nondefining clause.

Can I use that for a person?

Yes. Both who and that can refer to a person in a defining relative clause. Who often sounds more personal. Use who, not that, in a nondefining clause about a person.

Sources

• VOA Learning English: Identify With Relative Pronouns — explains who, that, and which, identifying versus extra information, commas, and object-pronoun omission.
• VOA Learning English: Adjective Clauses That Describe Places — explains place clauses with where and related preposition patterns.
• MLA Style Center: Restrictive and Nonrestrictive Modifiers — explains how essential meaning and punctuation distinguish the two clause types.
• VOA Learning English: Learning Participial Phrases — shows how participial phrases can function as shortened relative clauses.