Sentences

Noun Clauses

Roger Fielding Published 18 July 2026 · 9 min read Adult

🎒 Teaching an 8–18-year-old? Read the young-learner edition →

You're halfway through an email to your manager:

I think that the main reason the project slipped was…

and you pause, wondering why this sentence has turned into a snake. There's a whole run of words after that, and you can feel it hanging together as one idea — but if someone asked you, "What's the subject here? What's the object?" you'd probably mutter something unprintable and go and make more coffee.

Let's be honest — once sentences start nesting inside each other like this, most of us were never actually shown what's going on underneath. We just picked up the patterns by ear, the way you pick up which fork to use, and hoped nobody asked us to explain it.

The good news is, there's a clear way to see the structure sitting under all this. A lot of those "snake" bits are noun clauses — whole clauses behaving as if they were a single noun, stepping into the role of subject, object, or complement. Once you can spot them, you'll write with a lot more confidence: careful explanations, reports, firm-but-polite emails (I'm afraid that what you're asking isn't possible), any sentence where you need to say "this whole situation is the thing I mean."

We'll look at how these clauses work, why English so often hooks them onto a dummy it, and exactly where people tend to slip up.

Before you read on, here's where we're heading. By the end you'll be able to: - Recognise noun clauses and say what job they're doing. - Use that-clauses, wh-clauses, and if/whether-clauses as subjects, objects, and complements. - Reshape heavy sentences with "dummy it" so they read more naturally. - Avoid the common errors with missing that and question-style word order.

Beginner (Foundation): What Exactly Is a Noun Clause?

You already know nouns: job, idea, coffee, honesty, invoice. They do three jobs:

subjects: Honesty is important.
objects: We value honesty.
complements: Our main value is honesty.

Now look at this:

That we finished on time was a surprise.
We value that we finished on time.
The main thing is that we finished on time.

In each case, that we finished on time sits exactly where a simple noun could sit. That's your noun clause. A clause, remember, is any chunk with its own subject and verb — the server failed, costs are rising, we can't agree. A noun clause is a clause doing a noun's job — answering the same questions a noun would:

What do you think? → I think that this is fair.
What surprised you? → That we passed surprised me.
What is clear? → It's clear that we need more staff.

The three families you'll meet constantly

That-clauses - I agree that the deadline is unrealistic. - We accept that mistakes were made.

In speech and informal writing, that often just vanishes: I agree the deadline is unrealistic.

Wh-clauses (what, who, where, when, why, how, which) - I don't know why he left. - Please explain what you did. - We've agreed how we'll handle complaints.
If/whether-clauses - We're not sure if the figures are accurate. - I'd like to discuss whether this is worth the cost.

Each bold chunk is acting like "something" in the sentence — a thing you think, know, accept, explain, discuss. Try the pronoun test: swap it for it or that, and if the sentence still holds, you've got a noun clause.

Common Mistake: Treating any clause with that or what as a noun clause. It only counts if the whole chunk is functioning where a noun could go — subject, object, or complement — not merely linking two ideas together (that job belongs to subordinating conjunctions, covered in Pillar 2).

Quick recap: - A noun clause is a clause acting like a noun. - It can be a subject, object, or complement. - Common starters: that, what, who, where, when, why, how, if, whether. - Swap the chunk for it or a simple noun — if the sentence still works, you've found one.

Intermediate (Development): Subjects, Objects, and Complements

Now let's put these clauses to work — this is where your sentences start to feel controlled instead of runaway.

1. Noun clauses as objects

The most common pattern by a mile, and you already use it constantly:

I think that this is a mistake.
She realised that the email was unclear.
We can't decide whether we should raise our prices.
Tell me what you found.

Ask: Think what? Realised what? Decide what? Tell me what? Every time, the answer is a whole clause — the noun clause object. This crops up constantly after verbs like think, know, believe, say, admit, realise, remember, forget, decide, ask, tell, explain, show, discover, wonder.

2. Noun clauses as subjects

Slightly more technical, but don't let the label put you off:

That the budget was cut caused major problems.
What you suggested makes sense.
Whether we get funding is still unknown.

Ask: What caused problems? What makes sense? What's still unknown? Each answer is a whole clause acting as the subject.

These sound noticeably formal — and in speech we usually dodge them because a long subject at the front of a sentence just feels heavy. We reach instead for the dummy it pattern, coming up next. But it's worth being able to recognise the bare subject form, especially in reports:

That sales fell is obvious from the chart.
Whether the policy worked remains unclear.

3. Noun clauses as complements

A complement follows a linking verb — be, seem, become, remain, appear — and completes the idea started by the subject. Noun clauses do this brilliantly:

The truth is that we're over budget.
My concern is that the data may be wrong.
The issue is whether the benefits justify the cost.
Our question is how we can speed this up.

There's a pattern worth pinning to the fridge: abstract noun + be + that/if/whether/wh- clause. Once you spot it, you'll see it in every second paragraph of a formal report:

Our conclusion is that further testing is necessary.
The key question is whether this approach is sustainable.

4. The "dummy it" pattern (extraposition)

Here's the genuinely useful bit. A long clause at the front of a sentence sounds top-heavy. So English does something rather clever: instead of

That the server crashed again annoyed everyone.

we normally say

It* annoyed everyone that the server crashed again*.

It here is a dummy subject — a placeholder that carries no meaning of its own. The real subject is the clause sitting at the end: that the server crashed again. More examples:

It's clear that we need more time. (instead of That we need more time is clear.)
It surprised me how quickly they replied. (instead of How quickly they replied surprised me.)
It doesn't matter whether you email or call. (instead of Whether you email or call doesn't matter.)

This pattern — it + verb + [rest of sentence] + real subject clause — is everywhere in business and academic writing, because it lets you open with something light and deliver the weight of the sentence at the end, where the reader's ready for it.

Common Mistake: Calling it in It's clear that… the "subject" and forgetting the clause at the end entirely. Technically, it is just a dummy. The that-clause is where the real meaning lives.

Quick recap: - As objects, noun clauses answer "X what?" after verbs like think, know, explain. - As subjects, they can open a sentence, though we usually soften them with dummy it. - As complements, they complete ideas after linking verbs (The problem is that…). - The dummy it pattern turns heavy sentences into readable ones.

Advanced (Mastery): Finer Points and Style Choices

If you're still with me, you're ready for the subtler stuff — the bits that separate "basically correct" from genuinely confident and controlled.

1. When can you drop that?

You can lose that in plenty of noun clauses:

We think that this will work. → We think this will work.
She said that she'd call later. → She said she'd call later.

Keep that when: - leaving it out risks a misread: He told me yesterday he was leaving (is yesterday when he told me, or when he's leaving?) vs He told me yesterday that he was leaving (clear). - the clause is long or dense: We believe that the most likely explanation for the delay is the change in regulations. - the register is formal — reports, academic writing, anything going to a client.

Drop that when the verb's short and common (think, say, know, believe, guess) and the context is informal — a quick email, a chat message. If in doubt, keep it. It never makes a sentence ungrammatical; it just occasionally makes it a touch stiffer.

Pro-Tip: Read the sentence in your head. If you naturally say that, keep it. If you naturally skip it and the sentence stays clear, leave it out.

2. Noun clause vs direct question — the trap nearly everyone falls into

Compare:

What did he say? → a question.
I didn't hear what he said. → a noun clause.

In a question, we flip the order: What did he say? — auxiliary before subject. In a noun clause, we go back to plain statement order: what he said (subject he before verb said, no did anywhere).

More pairs:

Where are they going? (question) → I don't know where they are going. (noun clause)
How does this work? (question) → Can you show me how this works? (noun clause)
Why did you leave? (question) → She didn't say why you left. (noun clause)

Common Mistake: Mixing the two: I don't know where are they going. It should be I don't know **where they are going. A quick test: if the clause opens the sentence and ends in a question mark, it's a question. If it's tucked inside another sentence with no question mark, it's a noun clause — and needs ordinary word order.

3. Objects vs complements — for anyone who likes precision

We accept that the schedule has slipped. → object of accept.
Our position is that the schedule has slipped. → complement after is.

The rule of thumb: object follows an action verb (accept, know, believe, decide, explain); complement follows a linking verb (be, seem, become, remain), completing the subject. Most working writers never need the labels — but it's the kind of distinction that matters if you're doing detailed grammatical analysis or hit it in an exam question.

4. Noun clauses inside more complex patterns

Once you can see them clearly, noun clauses start turning up inside grander structures. Cleft sentences (a full article lives in Pillar 6.2) use them for emphasis:

Plain: That you raised this issue helped.
Cleft: It* was that you raised this issue* that helped.

That you raised this issue is still doing noun-like work — it's just been pulled into a pattern built for focus. You don't need to produce these on demand. Just know that the same noun clauses you've learned here plug straight into more advanced sentence shapes later on.

5. Where noun clauses really earn their place: diplomacy and precision

Noun clauses shine when you need to sound measured rather than blunt — reports, proposals, anything where you don't want to sound like you're issuing an edict.

Compare:

This is wrong.
We believe that this is wrong.

The second version signals whose judgement this is, leaves room for discussion, and lands with less aggression. More examples:

The results suggest that our approach is working.
The data indicates that customers are leaving faster than before.
A key question is whether we can maintain this growth.

And they do quietly diplomatic work when you need to deliver something unwelcome:

I'm afraid that what you're asking for isn't possible.
It seems that there's been a misunderstanding.

Pro-Tip: If your writing sounds too blunt or too certain, try shifting a flat statement into a noun clause: You're wrong → I think that you're wrong. The plan failed → The evidence suggests that the plan failed.

Quick recap: - That is often optional in object noun clauses; keep it for clarity or formality. - Noun clauses that look like questions keep normal word order (I don't know why he left). - After action verbs they're objects; after linking verbs, usually complements. - Noun clauses plug into advanced patterns like cleft sentences. - They're excellent for precise, diplomatic, formal writing.

UK vs US Usage

Structurally, noun clauses behave the same way in UK and US English — same patterns with that, what, whether, if, same dummy it constructions, no genuine grammatical divide. The one real difference worth flagging: whether vs if. Formal UK writing leans a touch more reliably on whether — especially when a noun clause is the subject, follows a preposition, or introduces a genuine choice (decide whether to proceed). American usage is somewhat freer with if in the same slots, particularly in speech and informal writing, though whether remains the safer, more formal choice on both sides of the Atlantic. Beyond that one point, don't go looking for divergence that isn't there — the underlying grammar is identical.

Spelling, as ever, tags along for the ride:

It's clear that this colour [US: color] scheme works better.

Key Takeaways

A noun clause is a clause used where a noun could go.
Noun clauses commonly act as subjects, objects, or complements.
They often start with that, what, who, where, when, why, how, if, whether.
We often move long subject clauses to the end and use dummy it at the front.
Noun clauses use normal statement word order — not question order.

Check Your Understanding

Underline the noun clause and name its role (subject, object, or complement): We accept that mistakes were made.
Rewrite this sentence using dummy it: That the negotiations failed was disappointing.
Question or noun clause? a) Why did they leave? b) We don't understand why they left.
Correct the error: I'm not sure what is the best option.
Object or complement? Our main concern is that staff are exhausted.

Answer Key

Noun clause: that mistakes were made. It's an object of accept (accept what?).
It was disappointing that the negotiations failed.
a) Question. b) Noun clause (object of don't understand).
Correct version: I'm not sure what the best option is (normal word order inside the noun clause).
That staff are exhausted is a subject complement after the linking verb is.

Internal Links

Back to Pillar 2: Subordinating Conjunctions
Pillar 1.2: Objects and Complements
Pillar 1.3: Subject Complements
Pillar 3.0: (routing overview for clause structures)
Pillar 3.1
Pillar 6.2: Cleft Sentences
Forward to Verbs & Tenses: for reported-speech tense changes and the mandative subjunctive inside noun clauses