What is Postmodification?
Postmodification means adding information AFTER a noun to describe or identify it. One common way to do this is with a relative clause. A relative clause is a group of words that tells us more about a noun. It usually starts with a relative pronoun like 'who', 'which', 'that', or 'where'. For example: 'The book that I bought yesterday is excellent.' The relative clause 'that I bought yesterday' comes after the noun 'book' and gives us extra information about which book we are talking about.
Two Types of Relative Clauses
There are two important types: restrictive and non-restrictive clauses. A restrictive clause is essential — it identifies which person or thing you mean. You do NOT use commas. Example: 'The students who scored above 80% passed the exam.' Here, the clause tells us WHICH students passed. A non-restrictive clause adds extra, non-essential information. You USE commas before and after it. Example: 'My sister, who lives in Paris, is a teacher.' The clause tells us where she lives, but we already know who she is. Without this clause, the sentence still makes complete sense.
Common Relative Pronouns
Different relative pronouns work with different noun types. Use 'who' or 'that' for people: 'The woman who helped me yesterday was very kind.' Use 'which' or 'that' for things and animals: 'The car which my parents bought last year is blue.' Use 'where' for places: 'The office where I work is near the station.' You can also use 'whose' to show possession: 'The student whose homework was excellent received a prize.' At B1 level, 'that' is the most common and safe choice for things, and 'who' for people.
Restrictive vs Non-Restrictive Relative Clauses — Side-by-Side Comparison
| Dimension | Restrictive Relative Clause | Non-Restrictive Relative Clause |
|---|---|---|
| Purpose | Identifies or defines the noun — it restricts the noun's reference to a specific subset, making the noun's meaning more precise. The clause is essential to understanding which person or thing is meant. | Adds extra, supplementary information about a noun that is already fully identified. The clause is parenthetical and provides background detail rather than identification. |
| Comma Usage | No commas are used. The clause is written immediately after the noun without any punctuation separation, showing it is tightly integrated into the sentence meaning. | Always set off by commas (or dashes/parentheses). A comma appears before the relative pronoun and after the clause if the sentence continues, marking it as additional, removable information. |
| Omissibility | Cannot be removed without fundamentally changing the meaning or making the sentence unclear. Removing it leaves the reader unsure which specific person or thing is being discussed. | Can be removed without changing the core meaning of the sentence. The main clause remains grammatically complete and still refers to the same specific noun even without the extra detail. |
| Pronoun Choices | Can use who, whom, which, or that. In informal English, that is very common with both people and things. The relative pronoun can also be omitted (zero relative) when it is the object of the clause. | Uses who, whom, or which only. That is generally not used in non-restrictive clauses. The zero relative (omission of the pronoun) is not possible in non-restrictive clauses. |
| Positive Example | The student who studied hardest passed the exam. Here, the clause identifies which specific student is meant — the one who studied hardest — distinguishing them from other students. |
Maria, who studied hardest, passed the exam. Here, Maria is already fully identified by name; the clause simply adds the extra fact that she studied hardest. It could be removed without confusion. |
| Negative Example | Employees who do not meet targets will not receive a bonus. The clause restricts employees to only those who fail to meet targets — a specific group, not all employees. |
The annual bonus, which is not guaranteed, depends on company performance. The bonus is already identified as the annual bonus; the clause adds a clarifying but non-essential remark about its nature. |
| Question Example | Is the book that I ordered available yet? The clause tells us exactly which book is being asked about — the one the speaker ordered — not just any book. |
Have you read War and Peace, which is considered a classic? The title already identifies the book; the clause adds a widely known fact as extra commentary within the question. |
| Key Signal Words / Tests | Often introduced by that, who, or which. Test: ask "Does removing the clause change which noun I mean?" If yes, the clause is restrictive. Common with indefinite or general nouns (a man who…, all students who…). | Often introduced by who, whom, or which (never that). Test: ask "Is the noun already uniquely identified before the clause?" If yes, the clause is non-restrictive. Common with proper nouns, unique nouns, or nouns with definite articles referring to one specific item. |
Key Difference: A restrictive relative clause is essential — it defines and limits which noun is meant, cannot be removed without loss of meaning, uses no commas, and may use that or zero relative. A non-restrictive relative clause is supplementary — it adds optional extra detail about an already-identified noun, is always separated by commas, and never uses that or the zero relative form.
Formula
✔ Positive
Noun
+
+ relative pronoun (who/which/that/where)
+
+ verb phrase
+
= postmodified noun phrase
The book that I read last month was fascinating.
Examples
The teacher who teaches us English is very patient.
Restrictive clause · Identifies which teacher
My best friend, who I have known since childhood, lives abroad now.
Non-restrictive clause · Extra information, with commas
The laptop that you bought last week is already very slow.
Restrictive clause · Identifies which laptop
The company where my father works is hiring new staff.
Restrictive clause · 'where' used for place
Sarah, whose presentation won the competition, was awarded a scholarship.
Non-restrictive clause · Shows possession with 'whose'
The restaurant that serves Italian food has closed permanently.
Restrictive clause · Identifies which restaurant
When to use it
Academic Writing
Use relative clauses to provide precise definitions and identify which specific items or concepts you are discussing.
"The theory that Einstein developed in 1905 changed modern physics forever."
Everyday Conversation
Add extra details about people, places, or things in natural speech without repeating the noun.
"Did you meet the doctor who is working at the new clinic?"
News and Reports
Clarify which person or event you are referring to, especially when introducing new information.
"The building that was damaged in the fire has been rebuilt."
Character Descriptions
Add details about people's characteristics or backgrounds to help readers understand who you mean.
"The girl whose father is a musician dreams of performing on stage."
Signal words
who
whom
which
that
where
whose
when
Common Mistakes
✕
Wrong
The person which helped me was kind.
✓
Correct
The person who helped me was kind.
Use 'who' for people, not 'which'. 'Which' is only for things.
✕
Wrong
The movie that I watched it yesterday was excellent.
✓
Correct
The movie that I watched yesterday was excellent.
Do not repeat the noun with a pronoun inside the relative clause.
✕
Wrong
The students who studied hard they passed the exam.
✓
Correct
The students who studied hard passed the exam.
The relative clause already contains the subject; do not add 'they' again.
✕
Wrong
My friend Sarah who lives in London is visiting me.
✓
Correct
My friend Sarah, who lives in London, is visiting me.
Non-restrictive clauses need commas. Here, we already know who Sarah is.
✕
Wrong
The reason why I left early was important.
✓
Correct
The reason I left early was important.
With 'reason', you can omit the relative pronoun and just use the clause directly.
KEY TAKEAWAYS
What to Remember
- Postmodification adds descriptive information after a noun to identify or describe it more clearly.
- Relative clauses are the main tool for postmodification and begin with who, which, that, or where.
- Use who for people, which for things, and that for both people and things.
- The relative clause directly follows the noun it describes and provides essential or extra information.
- Omit the relative pronoun only when it is the object of the relative clause, not the subject.