A noun clause is a subordinate clause that functions as a noun — as a subject, object, or complement in a sentence, as described in the Cambridge Grammar. For example, in I know that she is right, the clause that she is right is a noun clause functioning as the object of know. Like nouns, noun clauses can be replaced by a pronoun (it, that, this). They always contain a subject and a finite verb and are introduced by that, a wh-word, or whether/if. They are one of the most important structures in advanced English.
That-Clauses
That-clauses are the most common type of noun clause. They are introduced by that, which is often optional as the object of a verb but not as the subject or after nouns:
- I think (that) she is right. (object — 'that' optional)
- The fact that he lied shocked everyone. (after a noun — 'that' required)
- It is important that you arrive on time. (after an adjective — 'that' required)
- That she passed delighted everyone. (subject — heavy; prefer: It delighted everyone that she passed.)
Wh-Clauses
Wh-clauses use question words (what, where, when, why, who, which, how) as noun clauses. The word order is statement order, not question order: What he said surprised me. I don't know where she went. Tell me why you did it.
Whether/If Clauses
Whether/if clauses introduce embedded yes/no questions: Whether she comes or not doesn't matter. I don't know if he is coming. Prefer whether when the clause is the subject, after prepositions, in formal writing, or with 'or not'.
Noun Clauses as Subjects
Noun clauses can be sentence subjects, but they are heavy. English prefers to move them to the end with a dummy 'it' subject (extraposition): That she passed delighted everyone. → It delighted everyone that she passed. What he said was untrue. (wh-clause subject — this is fine and common)
Common Mistakes
- Wrong: I don't know where is she. Correct: I don't know where she is. (statement order, not question order)
- Wrong: The question is if we can afford it. Correct: The question is whether we can afford it. ('whether' preferred as subject complement)
- Wrong: She said me that she was tired. Correct: She told me that she was tired. / She said that she was tired. ('say' does not take an indirect object)
Practice Exercises
Grammar Quiz
Identify and complete noun clause structures in context.
Cloze Dropdown
Fill in 'that', wh-words or 'whether' in noun clause gaps.
Complete the Sentence
Add correct noun clauses to complete sentences.
Unjumble
Reorder words to form correct noun clause sentences.
Practice What You've Learned
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Frequently Asked Questions
What is a noun clause?
A noun clause is a subordinate clause that functions as a noun in a sentence. Like a noun, it can be a subject (What she said was true), an object (I know that he left), or a complement (The issue is whether we agree). Noun clauses always contain a subject and a verb and are introduced by 'that', a wh-word, or 'whether'/'if'.
When is 'that' optional in a noun clause?
'That' can be omitted when the noun clause is the object of a verb: I think (that) she is right. She said (that) he had left. 'That' cannot be omitted when the noun clause is the subject: That she survived is remarkable (not: She survived is remarkable). 'That' is also kept after nouns (the fact that, the idea that, the news that) and after certain adjectives (It is important that you attend).
What is the difference between a noun clause and a relative clause?
A noun clause functions as a noun and can replace a noun phrase: I know what she said (= I know the answer). A relative clause modifies a noun and functions as an adjective: The woman who called was friendly (modifies 'woman'). The key test: can it be replaced by a pronoun or noun phrase? If yes, it is a noun clause.
What is the difference between 'whether' and 'if' in noun clauses?
'Whether' is preferred when the noun clause is the subject (Whether he comes or not is uncertain); after prepositions (It depends on whether she agrees); in formal writing; with 'or not'. 'If' is more common in informal speech as an object clause: I don't know if he's coming. Avoid 'if' as a subject clause or after prepositions.
What verbs are commonly followed by 'that'-clauses?
Reporting and mental verbs: think, believe, know, say, claim, argue, suggest, report, feel, fear, hope, wish, doubt, admit, deny, realise, notice, assume, expect, agree. Adjective constructions: It is important/vital/essential/clear/obvious/surprising/possible that... Some verbs take the subjunctive in formal English: It is essential that he be present.
Can a noun clause be the subject of a sentence?
Yes, but it often sounds awkward when long. That prices will rise is likely. In practice, English speakers prefer to move the noun clause to the end with a dummy 'it' subject (extraposition): It is likely that prices will rise. It remains unclear what he intends to do. This is very common in both formal and informal English.
What is the difference between a noun clause with 'what' and a relative clause with 'what'?
A noun clause with 'what' means 'the thing that': I know what you did (= I know the thing that you did). There is no antecedent noun. A relative clause with 'what' is not standard in English — use 'that/which' instead: the problem that you mentioned (not the problem what you mentioned). 'What' as a relative pronoun does not exist in standard English.
How are noun clauses used in academic writing?
Noun clauses are extremely common in academic prose, especially as complements of reporting verbs: The study found that... The data suggest that... Researchers argue that... It is important to note that... They are also used to introduce uncertainty: It is unclear whether... Whether this approach is effective remains to be seen. Mastering noun clauses is essential for academic register.
What is the subjunctive in noun clauses?
After verbs of recommendation, demand, suggestion, and importance, formal English uses the base form of the verb (infinitive without 'to') for all subjects — this is the mandative subjunctive: The doctor recommended that he rest. It is essential that she be informed. The committee insists that he resign. More common in American English; British English often uses 'should + infinitive' instead.
Are noun clauses tested in Cambridge and IELTS exams?
Yes. Noun clauses appear in all levels from B1 upwards. At FCE (B2), sentence transformation tests (She said she would come → She said that...) and word order in embedded questions are common. At CAE/CPE, the subjunctive in noun clauses is assessed. In IELTS Writing, sophisticated use of noun clauses after reporting verbs contributes to a higher band score.