Relative Clauses: Defining and Non-Defining

Imagine you are at a crowded wedding in Delhi, trying to point out your cousin to a friend. You might say, “The girl who is wearing the red lehenga is my cousin.” Here, the phrase “who is wearing the red lehenga” is essential because it helps your friend identify exactly which girl you mean among dozens of guests. On the other hand, if you say, “My sister, who is wearing a red lehenga, lives in London,” the information about the dress is just an extra detail because you only have one sister. In English, these pieces of information are called relative clauses, and mastering them is the difference between sounding like a beginner and sounding like a polished professional in a corporate office like Infosys or TCS.

1. Relative Pronouns

Before we look at the types of clauses, we must understand the “tools” we use to build them: relative pronouns. The choice of pronoun depends on whether we are talking about a person, a thing, or a place.

Relative Pronouns and Their Uses

Relative Pronoun	Used For	Example Sentence
Who	People (Subject)	The manager who hired me is very kind.
Whom	People (Object)	The client whom we met yesterday is from Mumbai.
Which	Things/Animals	The laptop which I bought last week is lagging.
That	People/Things	The car that Arjun drives is a hybrid.
Whose	Possession	The student whose father is a doctor won the prize.
Where	Places	This is the café where we had our first meeting.
When	Time	I remember the day when the results were announced.

2. Defining Relative Clauses

Defining relative clauses are essential to the sentence. If you remove the clause, the sentence no longer makes sense or its meaning changes completely. In these clauses, we do not use commas.

Key Rules for Defining Clauses:

1. No Commas: Never put a comma before or after a defining clause.
2. Using 'That': In defining clauses, we can use 'that' instead of 'who' or 'which'.
   Examples

   ✅ The book that I bought is on the table.
   ✅ The book which I bought is on the table.

3. Omitting the Pronoun (Contact Clauses): If the relative pronoun is the object of the clause, you can leave it out entirely. This is very common in natural speech.
   Examples

   ✅ The report that I submitted was long.
   ✅ The report I submitted was long.

3. Non-Defining Relative Clauses

Non-defining clauses add extra, non-essential information. We already know exactly which person or thing is being discussed. If we remove this clause, the main idea of the sentence remains clear. These clauses must be separated by commas.

Key Rules for Non-Defining Clauses:

1. Always Use Commas: Use a comma before the clause and one after it (unless it ends the sentence).
2. No 'That': You cannot use 'that' to start a non-defining clause. You must use 'who' for people and 'which' for things.
3. Cannot Omit Pronouns: You must always include the relative pronoun (who, which, whose, etc.).

Defining vs Non-Defining Clauses

Aspect	Defining Clause	Non-Defining Clause
Purpose	Identifies the noun	Adds extra information
Punctuation	No commas	Uses commas
Can use 'that'?	Yes	No
Can omit pronoun?	Yes (if object)	No

4. Special Relative Words: Whose, Where, and When

These words follow the same defining/non-defining rules but have specific uses. Note that whose is a relative pronoun (showing possession), while where and when are relative adverbs — they replace adverbial phrases of place and time rather than acting as subjects or objects.

• Whose: Shows possession. It replaces words like his, her, or their.
  Examples

  ✅ The company whose CEO resigned is facing a crisis. (Defining)
  ✅ Priya, whose brother is a pilot, wants to join the Air Force. (Non-defining)

• Where: Refers to a place. Note that if you use 'which', you often need a preposition like in or at.
  Examples

  ✅ This is the house where I grew up.
  ✅ This is the house which I grew up in.

• When: Refers to a time.
  Examples

  ✅ Diwali is the time when families come together.

5. Reducing Relative Clauses

In formal writing or fast speech, we often “shorten” relative clauses to make them more concise. This is very common in news reports and academic papers.

• Active Voice: If the clause is in the active voice and the relative pronoun is the subject of the clause, replace who/which/that + the verb with a present participle (-ing form).
  Examples

  ✅ The man who is sitting by the window is my uncle.
  ✅ The man sitting by the window is my uncle.

• Passive Voice: If the clause is in the passive voice, replace who/which/that + be verb with a past participle (-ed/V3 form).
  Examples

  ✅ The documents which were signed by the director are on the desk.
  ✅ The documents signed by the director are on the desk.

6. Common Mistakes by Indian Learners

Many Indian learners translate directly from their native languages, leading to specific errors in relative clauses.

Common Errors and Corrections

❌ Incorrect	✅ Correct	Why?
Rahul is the boy which won the match.	Rahul is the boy who won the match.	‘Which’ is for things; ‘who’ is for people.
My sister, that lives in Delhi, is a doctor.	My sister, who lives in Delhi, is a doctor.	‘That’ cannot be used in non-defining clauses (with commas).
The hotel where we stayed at was cheap.	The hotel where we stayed was cheap.	‘Where’ already includes the idea of ‘at/in’. Don’t use both.
The person who I gave the file is Neha.	The person to whom I gave the file is Neha.	Don’t forget the preposition if the verb requires it.
The laptop what I bought is not working.	The laptop that/which I bought is not working.	’What’ cannot be used as a relative pronoun to refer back to a noun. Use ’that’ or ’which’ for things.

Summary

Relative clauses allow us to combine short, choppy sentences into sophisticated, flowing English. Whether you are writing an email to a manager or appearing for an IELTS speaking test, using these correctly shows high proficiency.

• Use who for people and which for things.
• Use whose for possession, where for places, and when for time.
• Defining clauses are essential and have no commas.
• Non-defining clauses are extra and must have commas.
• That is a versatile backup for defining clauses only.
• You can reduce clauses using -ing or -ed forms for a more professional tone.

Key takeaway: Always double-check your commas—they aren’t just decorations; they tell your reader whether the information is a vital detail or just a little something extra. Try writing five sentences about your family members today using non-defining clauses!