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Relative adverbs are three small words — where, when and why — that join two ideas neatly together. Instead of saying the village; I was born in that village, you say the village where I was born. They make your English smoother and more natural, and once you understand the pattern, they are surprisingly easy to use.
This guide explains what each relative adverb does, how they replace the more formal preposition + which, how they behave in defining and non-defining clauses, and how they differ from relative pronouns like who, which and that. Along the way you will find many example sentences and a clear list of the mistakes to avoid.
Key Takeaways
- Where follows a place noun, when follows a time noun, and why follows the noun reason.
- Each relative adverb is a shorter form of preposition + which: the day on which = the day when.
- In defining clauses, when and why can often be left out or replaced by that.
- In non-defining clauses (after a comma) the relative adverb must stay and cannot become that.
- The biggest mistake is using where with a noun that is not a real place.
The Three Relative Adverbs at a Glance
Each relative adverb matches a particular kind of noun — a place, a time, or a reason. Get the match right and the rest follows naturally.
| Relative adverb | Refers to | Replaces | Example |
|---|---|---|---|
| where | a place | in / at / on which | the hotel where we stayed |
| when | a time | on / in / at which | the day when we met |
| why | a reason | for which | the reason why she left |
Where — for places
Use where after a noun that names a place: a town, a room, a country, a building.
This is the house where I grew up.
The cafe where we first met has closed down.
She works in an office where nobody talks.
When — for times
Use when after a noun that names a time: a day, a year, a moment, a period.
I still remember the day when we moved house.
1990 was the year when everything changed.
There are moments when silence is best.
Why — for reasons
Use why after the noun reason (and only that noun, in practice).
Tell me the reason why you are late.
That is the reason why the shop is shut.
I do not understand the reason why he refused.
Replacing Preposition + Which
The clearest way to understand relative adverbs is to see them as a shortcut. Formal English often uses preposition + which; relative adverbs do exactly the same job in fewer words and a friendlier tone.
| Formal: preposition + which | Natural: relative adverb |
|---|---|
| the day on which we met | the day when we met |
| the place at which we waited | the place where we waited |
| the house in which she lives | the house where she lives |
| the reason for which he left | the reason why he left |
If you can rewrite a clause as preposition + which, you need a relative adverb. The office in which I work → the office where I work. This test stops you from wrongly using which on its own.
Defining vs Non-Defining Clauses
Relative adverbs appear in two kinds of clause, and the difference changes the punctuation and what you can leave out.
Defining clauses
- Identify which place, time or reason is meant.
- No commas.
- The town where I was born is tiny.
- The adverb can often be left out or replaced by that.
Non-defining clauses
- Add extra, non-essential information.
- Always use commas.
- We visited Bath, where the Roman baths still stand.
- The adverb must stay; that is impossible.
In 1969, when the first Moon landing happened, the world watched. (non-defining)
The year when the first Moon landing happened was 1969. (defining)
In 1969, that the first Moon landing happened, the world watched. (that is not allowed here)
Omitting the Adverb or Using That
In defining clauses, everyday English frequently drops when and why, especially after common nouns such as day, time, year and reason. You can also swap the relative adverb for that.
| Full form | With that | Adverb omitted |
|---|---|---|
| the day when we met | the day that we met | the day we met |
| the reason why he left | the reason that he left | the reason he left |
| the place where we stayed | the place that we stayed at | the place we stayed |
Dropping where is less common than dropping when or why, but it does happen after general place words like place, somewhere and everywhere: Is there anywhere we can sit? Remember that this freedom belongs only to defining clauses — never to clauses set off by commas.
The Reason Why vs The Reason That
Learners often ask whether the reason why is correct, since reason and why seem to repeat the same idea. All of these are standard and natural:
The reason why I called was to apologise.
The reason that I called was to apologise.
The reason I called was to apologise.
Some careful writers prefer the reason or the reason that to avoid the slight overlap, but the reason why is fully accepted in both spoken and written English. Choose whichever sounds best in your sentence.
Relative Adverbs vs Relative Pronouns
It is easy to confuse relative adverbs (where, when, why) with relative pronouns (who, whom, which, that). The difference is what they stand in for.
Relative pronouns
- Replace a person or a thing.
- Act as subject or object.
- the writer who won the prize
- the book that I read
Relative adverbs
- Replace an idea of place, time or reason.
- Equal to preposition + which.
- the city where I live
- the day when I arrived
A common trap is choosing which when you actually need a relative adverb. Compare: the house which I bought (correct — which is the object of bought) versus the house where I live (correct — where means in which). You would not say the house which I live, because a place needs where or in which.
Where vs In Which
After a place noun, where and in which mean the same thing but differ in formality. Where is the everyday choice; in which suits academic, legal or very formal writing.
This is the laboratory where the tests are carried out. (natural)
This is the laboratory in which the tests are carried out. (formal)
Both are correct, so let your tone decide. In an essay or report, in which can sound more precise; in conversation, where is almost always better.
Common Mistakes with Relative Adverbs
Most errors come from one habit: stretching where to cover nouns that are not really places.
This is a situation where we must be careful. → better: a situation in which we must be careful.
There is a part in the contract where it says this. → better: a part in which it says this.
the day which we met → correct: the day when we met.
the place where I live in → correct: the place where I live. (where already includes in)
Use where only with genuine places. For abstract nouns like situation, case, point or respect, prefer in which. And never add a second preposition after where — it is built in.
Practise Relative Adverbs
Put where, when and why into action with quick, interactive exercises.
Start PractisingExercises to Practise on LexFizz
- Flash Cards — review where, when and why with spaced repetition
- Quiz — multiple-choice questions on relative adverbs
- Complete the Sentence — fill the gap with the right relative adverb
- Cloze Dropdown — choose where, when or why from a dropdown
- Match Up — match each noun to its relative adverb
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Frequently Asked Questions
Relative adverbs are the words where, when and why. They introduce a relative clause and refer back to a noun that names a place, a time or a reason: the town where I grew up, the day when we met, the reason why she left. Each one replaces a longer structure of preposition + which — for example, the place in which becomes the place where. They are called adverbs because they describe place, time or reason, not because they replace a person or thing the way a relative pronoun does.
Each relative adverb matches a different kind of noun. Use where after a place noun: the city where I live. Use when after a time noun: the year when we married. Use why after the noun reason: the reason why he resigned. If you choose the wrong one — for example where after a time noun — the sentence sounds wrong to native speakers, so always match the adverb to what the noun describes.
Relative adverbs are a shorter way of saying preposition + which. The day on which we met means the same as the day when we met. The house in which she lives means the same as the house where she lives. The reason for which he left means the same as the reason why he left. The preposition-plus-which form is correct but formal; the relative adverb is more natural in everyday English.
A relative pronoun (who, whom, which, that) stands in for a person or a thing and can act as the subject or object of its clause: the book that I read. A relative adverb (where, when, why) stands in for an adverbial idea of place, time or reason, and is equal to a preposition plus which: the place where I work equals the place at which I work. A simple test: if you can rewrite the clause as preposition plus which, you need a relative adverb, not which alone.
Often yes, in defining clauses and informal English. The day that we met and the day when we met are both natural; the reason that he left and the reason why he left are both common. With that, the preposition is usually dropped: the house that I live in. You cannot use that in non-defining clauses, and you cannot replace where, when or why with that after a comma.
In defining relative clauses, when and why are often left out, especially after common nouns like day, time, year and reason: the day we met, the reason he left. The omission of where is less common but possible after place, somewhere or everywhere: the place we stayed. You cannot omit the relative adverb in a non-defining clause — that is, after a comma — where it must always appear in full.
The reason why, the reason that and simply the reason all introduce an explanation, and all three are correct: the reason why I called, the reason that I called, the reason I called. Some writers feel the reason why is slightly repetitive because reason and why overlap, but it is fully standard and very common. In careful writing you can choose the reason or the reason that if you prefer to avoid the repetition.
Where and in which mean the same thing after a place noun, but they differ in register. Where is natural and common: the office where I work. In which is more formal and is preferred in academic or legal writing: the office in which I work. Both are correct, so choose where for everyday English and in which when you want a more formal tone.
Yes. Where, when and why all appear in non-defining clauses, which add extra information and are set off by commas: We visited Bath, where the Roman baths still stand. In 1969, when the first Moon landing happened, millions watched on television. In a non-defining clause the relative adverb cannot be replaced by that, and it cannot be left out.
The most frequent mistake is using where with a noun that is not a place: writing the situation where instead of the situation in which, or the book where it says rather than the book in which it says. Where belongs only with real place nouns. Other errors include using which where you need a relative adverb (the day which we met instead of the day when we met) and adding an extra preposition (the place where I live in, where in is unnecessary because where already contains it).
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