Understanding Relative Clauses With “Who”, “That”, “Which”
Have you ever read a sentence that gave extra information about a person, thing, or idea without starting a new sentence?
That’s a relative clause at work. Relative clauses are groups of words that describe or identify nouns. They often begin with words like “who,” “that,” or “which.”
These words are called relative pronouns because they relate to something already mentioned in the sentence.
Understanding how and when to use “who,” “that,” and “which” correctly is a basic but powerful skill in English.
These words help people form longer, more descriptive, and more accurate sentences without confusion or repetition. They are essential in both spoken and written English across all education levels and professions.
Linguists from Cambridge University highlight that mastering relative clauses improves reading comprehension and helps students process complex ideas in a single sentence.
Studies in applied linguistics also show that learners who grasp relative pronouns early on make fewer grammatical mistakes in formal writing.
Let us now explore how each of these relative pronouns works, how they differ, and how to use them naturally and correctly in everyday English.
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What Does “Who” Mean in Relative Clauses?
“Who” is a relative pronoun that refers to people. It tells us more about a person or group of people mentioned earlier in the sentence. It acts as the subject of the relative clause and helps combine ideas smoothly.
Example 1:
The teacher who explains patiently is loved by the students.
This sentence gives extra information about the teacher. “Who explains patiently” tells us which teacher is being talked about.
Example 2:
My brother who lives in Abuja just got married.
Here, “who lives in Abuja” describes my brother and helps us know which brother is being referred to.
Example 3:
She hired a nanny who speaks French fluently.
This adds an important detail about the nanny. The person being hired has a skill relevant to the situation.
Example 4:
The woman who helped me was very kind.
This clause identifies the specific woman being talked about. It’s not just any woman but one who helped.
According to academic studies in second language acquisition, learners tend to understand “who” more quickly than other relative pronouns because it links directly with people, which is a clear and common concept in language.
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When Should You Use “That” in Relative Clauses?
“That” is more flexible than “who” or “which.” It can refer to people, animals, or things, depending on the sentence.
It is most often used in defining relative clauses, where the information is essential to the meaning of the sentence.
A defining relative clause tells us exactly which person or thing we are talking about. Without this clause, the meaning of the sentence would change or become unclear.
Example 1:
The car that broke down belongs to my uncle.
Without the clause “that broke down,” we would not know which car is being referred to.
Example 2:
The man that called you is waiting outside.
In this sentence, “that called you” identifies a specific man.
Example 3:
She lost the phone that her mother bought for her.
This describes a specific phone, not just any phone.
Example 4:
The story that he told us was unbelievable.
The relative clause gives us more information about the story and helps us understand which story it was.
Some grammarians believe “that” is more neutral than “who” or “which” and recommend using it in essential clauses to keep writing concise and fluid.
In informal writing or speech, “that” is often preferred, while in formal contexts, “who” and “which” may appear more frequently.
How Do You Use “Which” in Relative Clauses?
“Which” refers to animals or things, not people. It is used to give extra or non-defining information that is not crucial to the meaning of the sentence.
When using “which” in this way, you always add commas before and after the clause if it is in the middle of a sentence. Non-defining relative clauses can be removed without changing the main meaning of the sentence.
Example 1:
The house, which was built in 1950, needs repairs.
Here, “which was built in 1950” gives extra information about the house but isn’t essential.
Example 2:
She gave me a book, which I found very interesting.
The sentence would still make sense if we removed the clause “which I found very interesting.”
Example 3:
His laptop, which he bought last month, is already broken.
The clause provides detail but is not necessary to identify the laptop.
Example 4:
They adopted a dog which had been abandoned.
Here, the clause is defining. In British English, “which” can be used in defining clauses like this, but in American English, “that” is preferred.
Linguistic journals confirm that understanding when to use “which” and when to use “that” helps reduce sentence ambiguity. It also allows writers to signal clearly whether the clause is optional or essential to the meaning.
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How Can You Choose Between “That” and “Which”?
This is one of the most common questions in English grammar. The difference lies mainly in the type of clause you are writing.
If the clause defines or identifies the noun and cannot be removed without changing the sentence’s meaning, use “that”. If the clause simply adds extra detail that could be removed, use “which” and separate it with commas.
In American English, the rule is stricter:
Use “that” for essential clauses and “which” for non-essential clauses.
In British English, “which” can be used for both, although many style guides still recommend following the same rule for clarity.
Can You Omit the Relative Pronoun?
In some cases, yes. If the relative pronoun is the object of the clause, it can sometimes be left out.
Example:
The dress (that) she wore was beautiful.
“The dress she wore” is acceptable. “That” can be dropped.
But if the relative pronoun is the subject of the clause, it cannot be left out.
Example:
The man who saved the child is a hero.
You cannot remove “who” here because it is the subject of “saved the child.”
Does Punctuation Matter in Relative Clauses?
Yes. In non-defining clauses (usually introduced by “which”), use commas to separate the clause from the rest of the sentence. In defining clauses (usually using “that”), no commas are used.
This difference in punctuation helps the reader know whether the clause is essential to understanding the sentence or just adds detail.
Can Relative Clauses Come in the Middle or End of a Sentence?
Relative clauses usually follow the noun they describe. They can be in the middle or at the end of a sentence, depending on the structure.
Middle:
The woman, who was clearly upset, walked out of the room.
End:
He bought a shirt that didn’t fit him.
Placement depends on what is being described, but it must come immediately after the noun it refers to.
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Frequently Asked Questions About Relative Clauses
1. What is the main function of relative clauses in English?
Relative clauses add information about a noun. They help make sentences clearer, more specific, and more detailed without starting a new sentence.
2. Can I use “who” for animals?
No. “Who” is only used for people. For animals, use “that” or “which,” depending on the context.
3. What is the difference between defining and non-defining clauses?
Defining clauses give essential information needed to understand the sentence. Non-defining clauses add extra information and are separated by commas.
4. Can I use “that” instead of “which” all the time?
No. While some people use “that” in casual speech, in formal writing, “which” should be used for non-defining clauses with commas.
5. Are commas always needed in relative clauses?
Only non-defining clauses use commas. If the clause is essential (defining), do not use commas.
6. Why do Americans prefer “that” in some cases while British people use “which”?
It’s a matter of style and tradition. American English favors “that” for essential clauses and “which” for non-essential ones. British English is more flexible but is increasingly following the same pattern.
Final Thoughts
Learning to use “who,” “that,” and “which” correctly can change the way your English sounds. It helps you write and speak more clearly, accurately, and professionally.
Whether you are writing an essay, telling a story, or giving instructions, relative clauses make your language richer and more useful.
Just remember the key differences, pay attention to punctuation, and practice with real-life examples. Over time, your use of these important grammar tools will become second nature.