In “I know the answer,” the answer is a noun phrase. In “I know what she means,” the clause what she means fills the same position: it is the object of know.
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A noun clause is a traditional name for a dependent clause that functions in a position often occupied by a noun phrase. Learning its job in the sentence is more reliable than identifying it only by its first word.
Where noun clauses appear
A noun clause contains a subject and a verb, but it depends on a larger grammatical structure. In “What she said surprised me,” what she said is the subject of surprised; it is not a separate, independent sentence.
| Function | Complete sentence | Clause doing the job |
|---|---|---|
| Subject | What you decide matters. | What you decide |
| Object | I understand why you left. | why you left |
| Subject complement | The problem is that we have no time. | that we have no time |
| Complement of a preposition | We talked about what happened. | what happened |
You may hear a dependent clause alone as a conversational fragment, such as an answer to a question. That does not make it an independent clause in ordinary complete-sentence writing.
That-clauses: reporting a statement or idea
Use a that-clause after verbs such as think, believe, know, and explain. “I think that the office is closed” expresses the content of the thought.
After many common verbs, you can omit that: “I think the office is closed.” Keep it when it makes the structure clearer, especially in a longer sentence. A that-clause can also follow an adjective: “I’m glad that you called.”
When a that-clause is the subject, do not simply remove that. “That she remembered my name surprised me” is grammatical, although “It surprised me that she remembered my name” often sounds more natural.
Wh-clauses and embedded questions
Words such as what, where, why, when, who, and how can introduce clauses inside a larger sentence. An embedded question uses statement word order, even when the whole sentence is a polite question.
| Direct question | Embedded version |
|---|---|
| Where does she work? | I don’t know where she works. |
| Why did he leave? | Can you explain why he left? |
| What time is it? | Could you tell me what time it is? |
| Who called you? | I wonder who called you. |
Do not write “Can you tell me where is the station?” Use “Can you tell me where the station is?” The opening Can you tell me makes the full sentence a question; the embedded part keeps its subject before its verb.
When who is itself the subject, the order may look unchanged. “Who called?” becomes “I know who called,” with no extra subject or do-support.
Whether and if: questions with yes or no answers
Use whether or if to embed many yes/no questions: “Is the shop open?” becomes “I don’t know whether the shop is open” or “I don’t know if the shop is open.” These words introduce uncertainty about a possible answer.
Whether works in more grammatical positions. Use it before a to-infinitive, after a preposition, and in a clause used as the subject: “We discussed whether to wait,” “It depends on whether she agrees,” and “Whether we leave today is still undecided.”
With or not directly after the introductory word, use whether: “I don’t know whether or not he agrees.” You can also put or not at the end: “I don’t know if he agrees or not.”
Noun clause or relative clause?
A noun clause can fill a noun-like position itself. A relative clause usually adds information about a noun already present in the sentence.
| Sentence | What the highlighted clause does |
|---|---|
| I know what she bought. | Gives the content of what I know |
| I like the coat that she bought. | Describes the noun coat |
| I know where she lives. | Gives the information I know |
| I visited the town where she lives. | Describes the noun town |
The word that alone does not tell you which structure you have. In “I believe that she is right,” the clause expresses a belief; in “The book that she wrote is popular,” it identifies the book.
A short conversation
Lina: Do you know when the course starts?
Omar: The email says that it starts on Monday.
Lina: I’m not sure whether I can attend the first session.
Omar: Ask the tutor if a recording will be available.
Each dependent clause has a different introduction, but each supplies information required by the larger sentence. Notice when the course starts, not “when does the course start.”
Practice: identify and repair the clause
Complete the tasks before checking the explanations. For the rewriting questions, preserve the original meaning and use statement word order inside the new clause.
- Identify the noun clause: “What we need is a quieter room.”
- Correct: “I don’t know where does he live.”
- Embed “Why did the train stop?” after “Do you know…”
- Complete: “We haven’t decided _____ to stay or leave.” (if / whether)
- Which clause describes a noun: “I remember what you said” or “I remember the advice that you gave me”?
- Correct: “Could you tell me what is your name?”
- Can “That the train was late” normally stand alone as a complete written sentence?
- Embed “Did she receive the message?” after “I wonder…”
Answers and explanations
- What we need. It is the subject of is.
- I don’t know where he lives. Remove does and use the statement form lives.
- Do you know why the train stopped? The embedded clause has subject + past-tense verb.
- Whether. Use whether before to stay or leave.
- That you gave me. This relative clause describes the noun advice.
- Could you tell me what your name is? The subject your name comes before is.
- No. It is a dependent clause. Add a main structure, such as “That the train was late caused a problem.”
- I wonder if she received the message or I wonder whether she received the message. Both introduce an embedded yes/no question.
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