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Relative Clauses in English: Who, Which, That, and More

Relative Clauses in English: Who, Which, That, and More

Relative clauses add information about a noun inside one sentence. Instead of saying "I met a student. The student speaks three languages," you can say "I met a student who speaks three languages." The words "who speaks three languages" identify or describe the student.

Relative clauses make English more precise and natural. They help you describe people, objects, places, times, and possessions without repeating the same noun. This guide explains relative words, defining and non-defining clauses, punctuation, pronoun omission, and common errors. For a broader foundation, review Sentence Structure: How to Build Clear Sentences.

What Is a Relative Clause?

A relative clause is a dependent clause that modifies a noun or noun phrase. It cannot usually stand alone. A relative word connects the clause to the noun that it describes, called the antecedent.

  • "The teacher who helped me was patient."
  • "The book that I bought is useful."
  • "This is the classroom where we practice speaking."

In the first example, "teacher" is the antecedent and "who helped me" is the relative clause. The complete sentence has one main clause and one dependent clause.

The most common relative words are:

  • "who" and "whom" for people
  • "whose" for possession
  • "which" for things and animals
  • "that" for people or things in defining clauses
  • "where" for places
  • "when" for times

How to Use "Who," "Whom," "Which," and "That"

Use "who" when a person is the subject of the relative clause.

  • "She is the student who asked the question."
  • "The teacher who explained the rule was clear."

Use "whom" when a person is the object. "Whom" is formal and is less common in everyday speech.

  • Formal: "The professor whom I contacted replied quickly."
  • Common: "The professor who I contacted replied quickly."

After a preposition in formal writing, "whom" remains standard: "The person to whom I spoke was helpful." Everyday English often moves the preposition to the end: "The person who I spoke to was helpful."

Use "which" for things or animals.

  • "This is the book which helped me understand grammar."
  • "The exercise, which took 20 minutes, was useful."

Use "that" for people or things in defining relative clauses.

  • "The class that starts at 9:00 a.m. is full."
  • "The student that won the award gave a speech."

"Who" is usually more natural for people, especially in writing. Do not use "that" in a non-defining clause.

A classroom entrance and CWC logo in the hallway of the new Los Angeles campus

Defining Relative Clauses

A defining relative clause identifies which person or thing the speaker means. The information is essential.

  • "The student who sits next to me is from Brazil."
  • "The book that you recommended is excellent."
  • "The lesson we studied yesterday was useful."

Do not put commas around a defining relative clause. Compare these meanings:

  • "Students who practice daily improve their fluency."

This sentence refers specifically to students who practice daily.

  • "The students, who practice daily, are improving their fluency."

This sentence refers to a known group of students and adds the information that all of them practice daily.

The choice between defining and non-defining is not only a punctuation choice. It changes what the sentence says.

Non-Defining Relative Clauses

A non-defining relative clause adds extra information about an already identified noun. The main meaning remains complete if you remove the clause.

  • "CWC, which is located in Los Angeles, welcomes English learners from many backgrounds."
  • "My classmate Ana, who speaks Spanish, helped me with the activity."
  • "The museum, which we visited on Friday, had a new exhibition."

Use a comma before and after a non-defining clause when it appears in the middle of a sentence. Use one comma when it appears at the end.

Do not use "that" in this structure:

  • Incorrect: "My notebook, that is blue, is on the desk."
  • Correct: "My notebook, which is blue, is on the desk."

Do not omit the relative pronoun from a non-defining clause. "The museum, we visited on Friday, had a new exhibition" is not standard.

Using "Whose," "Where," and "When"

Use "whose" to show possession. It can refer to people, organizations, and sometimes things.

  • "I met a student whose pronunciation improved quickly."
  • "She is the writer whose essay won the contest."
  • "We visited a school whose programs serve international learners."

Use "where" for a place when the relative clause means "in/at that place."

  • "This is the café where we studied."
  • "Los Angeles is a city where people use many languages."

Do not add another place preposition after "where." Say "the café where we studied," not "the café where we studied at."

Use "when" for a time.

  • "I remember the day when I gave my first presentation."
  • "Summer is a season when many students travel."

More formal alternatives use a preposition plus "which":

  • "This is the café in which we studied."
  • "I remember the day on which we met."

Subject and Object Relative Pronouns

Knowing whether the relative word is a subject or object helps you decide whether it can be omitted.

In "The student who called me is my classmate," "who" performs the action "called." It is the subject, so you cannot omit it.

  • Incorrect: "The student called me is my classmate."
  • Correct: "The student who called me is my classmate."

In "The student who I called is my classmate," "I" is the subject and "who" is the object of "called." In a defining clause, you can omit the object pronoun.

  • "The student I called is my classmate."
  • "The book that I bought is useful."
  • "The book I bought is useful."

You cannot omit an object pronoun immediately after a fronted preposition: "The person to whom I spoke" needs "whom." If the preposition moves to the end, everyday English allows omission: "The person I spoke to."

CWC student walking through the book tunnel at The Last Bookstore in Los Angeles

Relative Clauses with Quantifiers and Whole Ideas

Non-defining clauses can include expressions such as "some of whom," "many of which," and "none of which."

  • "The class has 15 students, many of whom speak more than one language."
  • "We completed five activities, two of which involved speaking."

"Which" can also refer to an entire earlier idea:

  • "She completed her presentation early, which reduced her stress."

Here, "which" refers to the fact that she completed the presentation early, not to the noun "presentation" alone.

Use this structure carefully. If the reference is unclear, divide the thought into two sentences. Clear pronoun use helps readers follow complex sentences.

Reduced Relative Clauses

Some relative clauses can be shortened. This is common in academic and professional writing.

An active clause can often become an "-ing" phrase:

  • Full: "Students who attend the workshop should arrive early."
  • Reduced: "Students attending the workshop should arrive early."

A passive clause can often become a past-participle phrase:

  • Full: "The assignments that were submitted yesterday have been graded."
  • Reduced: "The assignments submitted yesterday have been graded."

A clause with "be" plus an adjective or prepositional phrase can sometimes lose "who/which + be":

  • Full: "The students who are in Room 4 are taking a test."
  • Reduced: "The students in Room 4 are taking a test."

Reduction must preserve the meaning and make the modified noun clear. When in doubt, keep the full relative clause.

Common Relative Clause Mistakes

Using a double pronoun

  • Incorrect: "The book that I bought it is useful."
  • Correct: "The book that I bought is useful."

Using "what" after a noun

  • Incorrect: "The book what I bought is useful."
  • Correct: "The book that I bought is useful."

"What" means "the thing that," so it does not follow an antecedent: "What I bought is useful."

Using commas around essential information

  • Incorrect for identification: "The student, who sits near the window, is from Brazil."
  • Correct: "The student who sits near the window is from Brazil."

Using "that" in a non-defining clause

  • Incorrect: "The course, that begins Monday, is full."
  • Correct: "The course, which begins Monday, is full."

Leaving out a subject relative pronoun

  • Incorrect: "The teacher works here speaks French."
  • Correct: "The teacher who works here speaks French."

How to Practice Relative Clauses

Begin by combining two short sentences:

  • "I met a classmate. The classmate lives near campus."
  • "I met a classmate who lives near campus."

Next, describe objects and places around you. Use "which," "that," and "where." Then compare a defining sentence with a non-defining sentence and explain how the meaning changes.

For writing practice, underline every relative clause. Draw an arrow to its antecedent. Check three things: Is the reference clear? Is the information essential? Does the punctuation match the meaning? These habits strengthen overall English writing skills.

At Columbia West College (CWC), the integrated curriculum connects Grammar, Speaking, and Reading & Writing. Learners can study a structure and then use the same target English in communication. English Speaking Success (ESS) includes a daily 80-minute speaking class with 6 times more speaking practice than a typical listening and speaking class. Connection Questions encourage students to use target language naturally and spontaneously, which can support later recall.

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Use Relative Clauses in Real Communication

Relative clauses become useful when they serve a real purpose. Describe a person who influenced you, a place where you felt welcome, or an experience that changed your plans. Ask a partner follow-up questions and listen for relative words in the answer.

Try a one-minute presentation with these prompts:

  • "A person who helped me..."
  • "A place where I learned something..."
  • "An object that I use every day..."
  • "A day when I felt proud..."

CWC students also build professional speaking confidence through weekly presentations. Repeated speaking gives learners opportunities to notice whether a long sentence remains clear to a listener. For more sentence-level support, review English Grammar Rules.

CWC students experiencing an audio chair exhibit during a MOCA learning activity

FAQ

What is a relative clause?

A relative clause is a dependent clause that describes a noun or noun phrase. It often begins with "who," "whom," "whose," "which," "that," "where," or "when."

What is the difference between defining and non-defining relative clauses?

A defining clause identifies the noun and does not use commas. A non-defining clause adds extra information about an already identified noun and uses commas.

Can "that" refer to people?

Yes. "That" can refer to people in defining relative clauses, but "who" is often more natural, especially in formal writing. "That" cannot introduce a non-defining relative clause.

When can a relative pronoun be omitted?

You can often omit the relative pronoun when it is the object of a defining clause, as in "The book I bought." Do not omit a subject pronoun or a pronoun in a non-defining clause.

What is the difference between "who" and "whom"?

"Who" functions as a subject. "Whom" functions as an object. Everyday English often uses "who" instead of "whom," except after a fronted preposition in formal contexts.

Relative clauses help you connect ideas without sacrificing precision. At CWC, integrated grammar and communication practice helps learners use complex structures with confidence. Contact Columbia West College to explore English study in Los Angeles.