What is a cleft sentence in English?

It is a sentence that splits one clause into two so that one element is highlighted. The kettle whistled can become It was the kettle that whistled (an it-cleft) or What whistled was the kettle (a wh-cleft). The facts stay the same; the focus changes.

What is the difference between an it-cleft and a wh-cleft?

An it-cleft starts with dummy it plus be and puts the focused phrase next: It was the cello that needed tuning. A wh-cleft starts with a free relative, usually what, and puts the focused phrase after be: What needed tuning was the cello. It-clefts are especially good for correction (not X, Y); wh-clefts are especially good when the given information is a whole clause.

Can I say It are the students who are late?

No. The verb after it is always singular: It is the students who are late. Who are agrees with students, but is agrees with it. The same holds in the past: It was the students who were late, never It were.

Is What I did was to resign better than What I did was resign?

Both occur. The bare infinitive (resign) is more common in speech and in informal writing. The to-infinitive is a little heavier and more likely when the infinitive itself is long. Avoid a finite verb after this pattern: What I did was resigned is not a cleft.

Are cleft sentences formal?

They belong to both speech and writing. Spoken English uses them constantly to correct and to delay the news (What I meant was...). Written English uses them to steer the reader toward a contrast or a reason. What can sound stiff is stacking several clefts in a row, or using an it-cleft where a simple sentence would do.

English grammar · Advanced

Cleft Sentences: It-Clefts and Wh-Clefts for Emphasis

Written by Eleanor Whitfield, Lead English Curriculum Editor · Reviewed September 2026

A cleft sentence splits one simple idea into two clauses so that one piece of information sits in a highlighted slot. The two main patterns are the it-cleft (It was the kettle that whistled) and the wh-cleft or pseudo-cleft (What I heard was a kettle). English uses them to correct, contrast, or delay the new information until the end of the sentence.

It was the kettle that whistled, not the alarm.

it-cleft putting the kettle in the focus slot after was

What it is

A cleft takes a single clause (The kettle whistled) and cuts it in two so that one element is singled out. In an it-cleft, a dummy it plus a form of be introduces the focused element, and a that- or who-clause carries the rest: It was the kettle that whistled. In a wh-cleft, a free relative clause (usually with what) names the given information, and be plus the focused phrase delivers the news: What whistled was the kettle. The original meaning stays the same; what changes is which piece the listener is invited to treat as the point.

She emailed the supplier. It was the supplier that she emailed. What she did was email the supplier. (Same event; three different focus choices.)

How to spot it

Look for It is/was/will be followed by a noun, prepositional phrase, or time expression and then that, who, or which. For a wh-cleft, look for a clause starting with what, why, where, or how, then is/was, then the focused phrase.

It is the treasurer who signs the cheques. (it-cleft focusing the person)
It was on the ferry that they first spoke. (it-cleft focusing a place phrase)
What delayed the kiln was a power cut. (wh-cleft with what as the subject clause)
What she wants is a later shift. (wh-cleft focusing a noun phrase after is)

The that-clause of an it-cleft looks like a relative clause, and historically it is one, but you cannot drop that after a focused adverbial: It was yesterday that I found out, not It was yesterday I found out in careful style.

Cleft Sentences Quick Reference

The two main cleft patterns

Type	Pattern	Example
It-cleft, noun	It + be + noun + that/who + clause	It was the cello that needed tuning.
It-cleft, adverbial	It + be + time/place + that + clause	It was in March that the lease ended.
Wh-cleft, thing	What-clause + be + focused phrase	What I need is a quiet desk.
Wh-cleft, action	What + subject + do + be + (to) + verb	What they did was rewrite the brief.
Wh-cleft, event	What happened + be + (that) + clause	What happened was that the ferry turned back.
Negative it-cleft	It + be + not + focus + that-clause	It was not the rain that flooded the cellar.
Question it-cleft	Be + it + focus + that-clause	Was it the neighbour who reported it?
Reason cleft	Why-clause or the reason why + be + clause	Why she resigned was never explained.

Common Cleft Sentences Examples in English

Clefts grouped by the job they do, not by the word that starts them:

Correcting and Contrasting

It was the bass, not the drums, that drowned the vocal.: it-cleft used to correct a wrong guess
It isn't the price that worries me; it's the lead time.: negative it-cleft plus a follow-up contrast
What I objected to was the tone, not the proposal itself.: wh-cleft naming the real complaint
It was Maya who called, not the agency.: who after a focused person

This is the most common spoken use: someone has the wrong element in mind, and the cleft puts the right one in the spotlight.

Highlighting Circumstance

It was after midnight that the warehouse lights went out.: focused time phrase
It is from this platform that the coastal train leaves.: focused place phrase in the present
It was because of the frost that the pipes burst.: focused reason phrase with because of
It will be in October that the gallery reopens.: it-cleft with will be for a future focus

Time, place, and reason phrases take that after the focus, not which or who.

Naming the New Information

What the lab needs is a backup generator.: given: the lab needs something; new: a generator
What surprised us was how calm she stayed.: the focused element can be a whole clause
What we should do is wait for the tide.: wh-cleft giving advice by focusing the action
How they finished on time remains a mystery.: how-clause as a free relative, no dummy it

A wh-cleft is often the better choice when the given information is long and the news is a short phrase at the end.

Focusing the Action

What the committee did was postpone the vote.: did in the what-clause, bare infinitive after was
What she has done is alert the insurers.: perfect in the what-clause, bare infinitive after is
All they did was send a holding email.: all-cleft reducing the action to a minimum
It is rewriting the index that takes the time.: it-cleft focusing an -ing action as a noun

After What X did was, both a bare infinitive and a to-infinitive occur; the bare form is more common in speech.

How Cleft Sentences Work

Four facts about agreement, the relative word, and information structure cover almost every well-formed cleft.

It Agrees with It, Not with the Focus

The verb after it is always a form of be agreeing with dummy it: It is the volunteers who lock up, never It are the volunteers. The verb inside the that- or who-clause agrees with the focused noun: who lock up, because volunteers is plural. Tense on be is chosen for the time of the focused situation: It was, It is, It will be, It has been.

It is the interns who restock the shelves after closing.

is matches it; restock matches the interns

It is/was, then the clause verb matches the focus.

Choose That, Who, or a Bare Clause

After a focused person, who is the default and that is acceptable in a defining style: It was the janitor who found the keys. After a thing, that is unmarked and which is possible but heavier. After a focused time, place, or reason, that is required. In informal speech, that is sometimes dropped after a focused object (It was this key I used), but keeping that is never wrong.

It was this key that opened the side door.

that after a focused thing; who would be wrong here

Who for people, that for things and adverbials.

The Wh-Clause Is the Given, the Complement Is the News

A wh-cleft starts from information the listener already has (something was needed, something happened) and lands on the missing piece. That is why What we need is silence works when everyone knows a need exists, and why starting from the news (Silence is what we need) is a reverse wh-cleft with the opposite information flow. Do not put brand-new material in the what-clause; the clause will feel unmotivated.

What the neighbours complained about was the late rehearsals.

the complaint is given; late rehearsals is the news

Wh-clause = given. Complement = new.

What Happened Takes a Full Clause After Be

When the subject is What happened or What they did, the focused material after be is often a full finite clause, optionally introduced by that: What happened was (that) the sprinkler went off. A noun phrase is also possible (What happened was a power cut) but a second finite clause is the natural way to report an event. Avoid a second dummy it here: What happened was it that is not English.

What happened was that the sprinkler soaked the archive.

that-clause after was naming the event

What happened was (that) + full clause.

Common Mistakes with Cleft Sentences

Incorrect: It were the technicians who reset the server.

Correct: It was the technicians who reset the server.

Dummy it always takes a singular form of be. The plurality of technicians shows up on the verb in the who-clause (reset, or are resetting), not on was.

Incorrect: What I need is that a later shift.

Correct: What I need is a later shift.

A wh-cleft takes a noun phrase, an infinitive, or a full that-clause after be, not that plus a noun phrase. That appears when the complement is a finite clause: What I heard was that the ferry had sailed.

Incorrect: It was yesterday I have found the keys.

Correct: It was yesterday that I found the keys.

Two problems: the that after a focused time expression is needed in careful English, and the clause after it should not jump to the present perfect when the it-cleft is already in the past.

Incorrect: All what they did was to send a holding email.

Correct: All they did was send a holding email.

All is not followed by what. The relative clause after all takes that or nothing. A bare infinitive after was is the usual choice in this pattern.

All-Clefts and Reverse Wh-Clefts

Two close relatives of the wh-cleft, both common, both easy to overuse.

All-clefts

All I want/need/did is reduces the focused element to a minimum and often sounds like a defence or a modest request. The what-clause is replaced by all + a relative clause without a relative pronoun.

All I asked for was a written quote.: minimising the request
All they did was forward the complaint.: reducing their action to one step
All that remains is the signature.: all that, slightly more formal

All what I want is is not English; choose all I want or all that I want.

Reverse wh-clefts

The focused phrase comes first, then be, then the what-clause: A later shift is what she wants. This pattern points backwards at something just mentioned and is common at the end of a turn.

A backup generator is what the lab needs.: news first, given what-clause second
Rewrite the brief is what they should do.: bare action as the focused phrase, informal
That is why the ferry turned back.: that-cleft pointing at a reason just given

That is why/when/where/how... is a closed set of reverse clefts built on that rather than a full noun phrase.

It-clefts with when and where

When the focus is a time or place, some writers use when or where instead of that: It was 2019 when the studio opened. That remains the safer choice in careful prose, especially after a prepositional phrase (It was in 2019 that..., not where or when).

It was 2019 when the studio opened.: when after a bare year, acceptable
It was in the annex that they stored the prints.: that required after a prepositional place phrase
It was the annex where they stored the prints.: where after a noun place, like a relative clause

If the focus is a prepositional phrase, stay with that.

Quick Check: Cleft Sentences

Rewrite each sentence as the cleft named in brackets, keeping the meaning.

1. The cello needed tuning. (it-cleft focusing the cello)

Answer: It was the cello that needed tuning.

it + was + noun + that-clause

2. They postponed the vote. (wh-cleft with What they did)

Answer: What they did was postpone the vote.

did in the what-clause, bare infinitive after was

3. The neighbour reported it. (question it-cleft)

Answer: Was it the neighbour who reported it?

be + it, who after a person

4. I asked for a written quote and nothing more. (all-cleft)

Answer: All I asked for was a written quote.

all + clause, no what

5. The late rehearsals caused the complaint. (wh-cleft starting What the neighbours complained about)

Answer: What the neighbours complained about was the late rehearsals.

preposition about stays at the end of the what-clause

Cleft Sentences FAQs

What is a cleft sentence in English?: It is a sentence that splits one clause into two so that one element is highlighted. The kettle whistled can become It was the kettle that whistled (an it-cleft) or What whistled was the kettle (a wh-cleft). The facts stay the same; the focus changes.
What is the difference between an it-cleft and a wh-cleft?: An it-cleft starts with dummy it plus be and puts the focused phrase next: It was the cello that needed tuning. A wh-cleft starts with a free relative, usually what, and puts the focused phrase after be: What needed tuning was the cello. It-clefts are especially good for correction (not X, Y); wh-clefts are especially good when the given information is a whole clause.
Can I say It are the students who are late?: No. The verb after it is always singular: It is the students who are late. Who are agrees with students, but is agrees with it. The same holds in the past: It was the students who were late, never It were.
Is What I did was to resign better than What I did was resign?: Both occur. The bare infinitive (resign) is more common in speech and in informal writing. The to-infinitive is a little heavier and more likely when the infinitive itself is long. Avoid a finite verb after this pattern: What I did was resigned is not a cleft.
Are cleft sentences formal?: They belong to both speech and writing. Spoken English uses them constantly to correct and to delay the news (What I meant was...). Written English uses them to steer the reader toward a contrast or a reason. What can sound stiff is stacking several clefts in a row, or using an it-cleft where a simple sentence would do.