Chapter 13: Relative Clauses — who, which, that, where, when

Relative clauses add information about a noun. They are introduced by relative pronouns or adverbs, and knowing the difference between defining and non-defining clauses is key to correct punctuation and meaning.

Relative Pronouns and Adverbs

Pronoun/Adverb	Refers to	Example
who	people (subject)	The man who called* you is here.*
whom	people (object, formal)	The woman whom* I met was kind.*
which	things/animals	The book which* I borrowed was great.*
that	people/things (defining only)	The car that* I drive is old.*
whose	possessive (people/things)	The student whose* essay won is talented.*
where	place	The city where* I grew up is small.*
when	time	I remember the day when* we met.*
why	reason	I don’t know the reason why* he left.*

Defining vs. Non-Defining Relative Clauses

This is the most important distinction in relative clause grammar:

Type	Purpose	Punctuation	Can use that?
Defining	Identifies which specific noun is meant; essential to meaning	No commas	Yes
Non-defining	Adds extra, non-essential information about the noun	Uses commas	No

Defining: The student who studies hardest will succeed. (tells us which student)

Non-defining: Maria, who studies every night, passed the exam. (we already know which Maria; the clause just adds info)

Removing a defining clause changes the meaning. Removing a non-defining clause leaves the sentence intact.

Omitting the Relative Pronoun (Contact Clauses)

When the relative pronoun is the object of the defining clause, it can be omitted:

The book (that) I borrowed was excellent. ✅ (omission possible)
The man who called you is here. ✅ (cannot omit — who is the subject)

Reducing Relative Clauses

Relative clauses can be shortened to participial phrases:

Full clause	Reduced form
The woman who is standing* by the door…*	The woman standing* by the door…*
The car that was stolen* last week…*	The car stolen* last week…*

Common Mistakes

Using that in non-defining clauses: ❌ London, that is the capital, is huge. → ✅ London, which is the capital, is huge.
Double subject: ❌ The man who he called me… → ✅ The man who called me…
Missing comma in non-defining clause: ❌ My sister who lives in Paris visited us. → ✅ My sister, who lives in Paris, visited us.

Key Checklist

I can distinguish between defining and non-defining relative clauses and punctuate them correctly.
I know which relative pronouns to use for people, things, possession, place, and time.
I can reduce relative clauses to participial phrases for more concise writing.

Relative Clauses: who, which, that, where, when