Noun Clauses and How to Use Them: English Grammar Guide

What Is a Noun Clause?

A noun clause is a dependent clause that functions as a noun within a sentence. Because it acts like a noun, it can serve as a subject, object, or complement. It typically answers what?, who?, or whom?

Examples

• What she said surprised everyone. → (Subject)

• I don’t know where he went. → (Object)

• The problem is that we are late. → (Subject complement)

Common Words That Introduce Noun Clauses

Noun clauses usually begin with that, if, whether, or wh- words (who, whom, whose, what, which, where, when, why, how).

Examples

• I believe that she is honest.

• We’ll find out whether the store is open.

• She asked where I was going.

• I can’t remember what he said.

These are often called noun clause markers because they signal the start of a noun clause.

Noun Clauses as the Subject

A noun clause can be the subject, a pattern common in formal writing.

Examples

• What you decide will affect the whole group.

• That she passed the exam made her parents proud.

• Whether we arrive on time depends on the traffic.

In everyday English, we often use a dummy “it” and move the clause later:

• It surprised everyone that she passed the test.

• It is unclear whether they will attend.

This keeps sentences smooth and readable.

Noun Clauses as the Object

Noun clauses frequently function as the object of a verb.

Examples

• I know that she lives in セブ島 (Cebu).

• We don’t understand why he left early.

• She asked what time the class starts.

Here, verbs like know, understand, and ask take a clause as their object.

Noun Clauses as the Object of a Preposition

A noun clause can follow a preposition, serving as its object.

Examples

• We’re thinking about what we should do next.

• She’s worried about whether he’ll be on time.

• I’m interested in how the system works.

Don’t omit the preposition—without it, the sentence becomes ungrammatical.

Noun Clauses as a Subject Complement

A subject complement renames or explains the subject, often after linking verbs like be, seem, or become.

Examples

• The truth is that he lied.

• My question is why you didn’t call.

• The issue was whether we had enough time.

In each, the clause further identifies or clarifies the subject.

Noun Clauses as an Appositive

An appositive noun clause follows a noun and explains or defines it.

Examples

• The fact that he apologized surprised everyone.

• The question whether she will come remains unanswered.

• The idea that learning is fun motivates students.

Tip: Don’t confuse appositive clauses with relative clauses. An appositive identifies the noun; a relative clause describes it.

Noun Clauses Beginning with “That”

That often introduces noun clauses, but it’s sometimes optional in speech and informal writing.

Examples

• I think that he’s right. → I think he’s right.

• She said that she was tired. → She said she was tired.

Keep that in formal contexts or when omitting it might cause ambiguity.

Noun Clauses Beginning with “If” or “Whether”

Use if or whether to report yes/no questions, uncertainty, or alternatives.

Examples

• I don’t know if she will come.

• I wonder whether it’s true.

• Let’s see whether they can help us.

In more formal writing (especially with or not), whether is preferred:

• I don’t know whether or not he’ll agree.

Noun Clauses with Wh- Words

Wh- words (who, what, when, where, why, how, which) introduce clauses from wh- questions, but the internal word order becomes statement order, not question order.

Examples

• I don’t know who called me.

• Can you tell me where the restroom is?

• She explained how the machine works.

Word Order Reminder

• ❌ I don’t know where is she going.

• ✅ I don’t know where she is going.

Noun Clauses in Reported Speech

Noun clauses are central to reported (indirect) speech.

Examples

• Direct: “I am tired.” → Reported: She said (that) she was tired.

• Direct: “Where are you going?” → Reported: He asked where I was going.

The clause functions as the object of reporting verbs like say, tell, ask, explain, wonder.

Verbs and Adjectives That Commonly Take Noun Clauses

Certain verbs and adjectives regularly introduce noun clauses.

Common Verbs

• Mental/communication: say, tell, think, believe, know, wonder, ask, explain, admit, deny, suggest, insist, realize, remember, forget

  • She admitted that she’d made a mistake.

  • They wondered whether the plan would work.

Common Adjectives

• sure, certain, glad, sorry, aware, afraid, happy, surprised

  • I’m not sure whether this is correct.

  • We’re glad that you could join us.

Punctuation and Style Notes

• No comma before a restrictive noun clause introduced by that, if, whether, or a wh- word.

• Use that for clarity when multiple nouns or lengthy subjects might confuse the reader.

• In formal writing, avoid stacking multiple clauses without clear structure; consider splitting long sentences.

Common Errors to Avoid

1) Using question word order inside the clause

• ❌ I don’t know where is he.

• ✅ I don’t know where he is.

2) Forgetting the clause marker

• ❌ I wonder you are happy.

• ✅ I wonder if you are happy.

3) Misusing reporting verbs

• ❌ He said me that he was late.

• ✅ He told me that he was late. / He said that he was late.

4) Omitting necessary prepositions

• ❌ I’m thinking what to do. (in many cases)

• ✅ I’m thinking about what to do.

Practice: Identify the Noun Clause and Its Function

1. I can’t believe that you finished the project early. → (Object)

2. What you said hurt my feelings. → (Subject)

3. She asked me if I could help her. → (Object)

4. The fact that he’s leaving makes me sad. → (Appositive to “fact”)

5. Do you know where the bus station is? → (Object)

Try rewriting #1 using a dummy subject:

• It is unbelievable that you finished the project early.

Why Noun Clauses Matter

Mastering noun clauses lets you:

• Express complex thoughts clearly and precisely.

• Write in a more formal or academic style when needed.

• Integrate explanations and evidence smoothly without repetitive nouns.

• Report questions and statements naturally in conversation and writing.

Quick Reference Checklist

• Marker chosen correctly? (that / if / whether / wh-)

• Word order inside the clause = statement order

• Function identified? (subject, object, complement, appositive)

• Prepositions included when required? (about, in, on, for, etc.)

• Style: Keep that when clarity might suffer without it.

Conclusion

A noun clause is a versatile tool that can serve as a subject, object, complement, or appositive, typically introduced by that, if, whether, or wh- words. By choosing the right marker, maintaining statement word order, and placing the clause where it serves your meaning best, you’ll write and speak with greater nuance and fluency.

FAQs

What is a noun clause and how is it different from a noun phrase?

A noun clause is a dependent clause that functions as a noun. It contains a subject and a verb and is introduced by markers like that, if, whether, or wh- words (what, who, where, when, why, how). A noun phrase, by contrast, does not need a verb; it can be a single noun or a noun with modifiers (e.g., the new policy). Compare: I believe that the policy will change (noun clause) vs. I support the new policy (noun phrase).

Which words commonly introduce noun clauses?

Frequent markers include that, if, whether, and wh- words: who, whom, whose, what, which, where, when, why, how. Each signals a clause that can serve as a subject, object, complement, or appositive.

What functions can a noun clause perform in a sentence?

• Subject: What you decided helped the team.
• Object of a verb: She discovered that the file was missing.
• Subject complement: The point is that we must act.
• Object of a preposition: They argued about whether we should expand.
• Appositive: The idea that learning can be fun motivates students.

When can I omit “that” in a noun clause?

In informal writing and speech, that is often optional after reporting and mental verbs like say, think, believe, know: I think (that) it will rain. Keep that in formal contexts or where omission could cause ambiguity, especially when multiple nouns or long subjects appear near the clause.

Should I use “if” or “whether,” and is “whether or not” necessary?

Use whether for alternatives or when the clause implies a choice: We discussed whether the plan was feasible. Use if primarily for yes/no content: I’m not sure if it’s ready. In formal writing, prefer whether, especially before or not: We will proceed whether or not funding arrives. Avoid placing or not far from whether unless it improves clarity.

What is the correct word order inside a noun clause formed from a question?

Inside noun clauses, use statement word order (subject before verb), not question inversion. Correct: I don’t know where she is. Incorrect: I don’t know where is she. The wh- word triggers the clause, but the clause itself is structured as a statement.

How do noun clauses work in reported (indirect) speech?

Reported speech converts direct quotes or questions into noun clauses. For statements, use that (often optional): She said (that) she was tired. For questions, use wh- words or whether/if, and keep statement order: He asked where the station was; They wondered whether it would sell. Tense may shift according to sequence-of-tense rules, especially after past reporting verbs.

What verbs and adjectives commonly take noun clauses?

Common verbs: say, tell, think, know, believe, suspect, realize, remember, forget, explain, admit, deny, suggest, insist, wonder, ask. Common adjectives: sure, certain, aware, afraid, happy, glad, sorry. Examples: I am not sure whether this is necessary; They insisted that we arrive early.

How do I punctuate sentences with noun clauses?

• Do not place a comma before restrictive noun clauses introduced by that, if, whether, or wh- words.
• Use commas around an intervening appositive phrase if it’s nonessential, but this is rare with noun clauses because they typically function as integral sentence parts.
• Retain that when it reduces ambiguity in long or complex sentences.

What is an appositive noun clause and how is it different from a relative clause?

An appositive noun clause renames or defines a preceding noun (the fact, the idea, the belief, the claim): The belief that hard work pays off is widespread. A relative clause describes a noun and usually begins with who, which, that: The belief that many people share is encouraging. The appositive clause answers “what belief?”; the relative clause tells you more about the belief.

Can a noun clause be the subject, and is there a more natural alternative?

Yes, a noun clause can be a subject: What she accomplished was impressive. In many contexts, English prefers a dummy subject it and postpones the clause: It was impressive what she accomplished. This extraposition improves flow, especially when the clause is long.

How do noun clauses function as objects of prepositions?

Prepositions can take noun clauses as objects when followed by wh- or whether/if clauses: We talked about what we should prioritize; They’re concerned about whether costs will rise. Keep the preposition—dropping it often yields ungrammatical or awkward structures.

What are common mistakes to avoid with noun clauses?

1. Question inversion inside clauses: ❌ I wonder where is he → ✅ I wonder where he is.
2. Missing clause marker: ❌ I wonder you are ready → ✅ I wonder if you are ready.
3. Misusing reporting verbs: ❌ He said me that… → ✅ He told me that… / He said that….
4. Omitting necessary prepositions: ❌ I’m thinking what to do (often incomplete) → ✅ I’m thinking about what to do.
5. Ambiguity from dropping “that”: Reinsert that if the sentence becomes confusing.

How do tense and pronoun changes work in reported clauses?

After a past reporting verb, the clause often backshifts tense: “I am busy” → She said (that) she was busy. Pronouns and time words shift from the speaker’s perspective to the reporter’s: “I’ll finish this tomorrow” → He said he would finish it the next day. Keep present tense if the statement is still true or expresses a general fact.

Can noun clauses be reduced like other clauses?

Noun clauses are not typically “reduced” in the same way as adverbial or relative clauses. However, writers sometimes replace a noun clause with an infinitive or gerund phrase when meaning allows: We decided to postpone (instead of We decided that we would postpone). Use reductions only if clarity and accuracy are preserved.

How can I make long sentences with multiple noun clauses clearer?

Use that for clarity, break complex sentences into two, and consider extraposition with it. Parallel structure also helps: We concluded that the costs were rising, that the timeline was tight, and that additional staff were necessary. Keep each clause structurally similar.

What quick checks ensure my noun clause is correct?

• Marker: Correct choice (that/if/whether/wh-)?
• Order: Statement order inside the clause?
• Function: Does the clause clearly act as subject, object, complement, object of preposition, or appositive?
• Clarity: Would keeping that remove ambiguity?
• Punctuation: Avoid unnecessary commas before restrictive clauses.

Can you give practice items with answers?

1. Identify the noun clause and its function:
   “I can’t believe that you finished early.” → Noun clause as object of believe.
2. “What you proposed seems reasonable.” → Noun clause as subject.
3. “We’re unsure whether the data is valid.” → Noun clause as object of adjective unsure.
4. “The problem is that our estimates were optimistic.” → Noun clause as subject complement.
5. “They talked about how the system works.” → Noun clause as object of preposition.

What’s the bottom line on using noun clauses well?

Choose the right marker, maintain statement order, use that when clarity demands it, and place the clause where it best serves your meaning. With these habits, noun clauses let you express complex, precise ideas—essential for academic, professional, and polished everyday communication.

English Grammar Guide: Complete Rules, Examples, and Tips for All Levels