A noun clause is a dependent clause that functions as a noun within a sentence. Just as a single noun can serve as a subject, object, or complement, a noun clause—an entire group of words containing a subject and verb—can fill those same roles. Noun clauses are essential for expressing complex ideas, reported speech, and embedded questions. This guide covers everything you need to know about noun clauses, from basic definitions to advanced usage patterns.
Table of Contents
- What Is a Noun Clause?
- Words That Begin Noun Clauses
- Noun Clauses as Subjects
- Noun Clauses as Direct Objects
- Noun Clauses as Indirect Objects
- Noun Clauses as Subject Complements
- Noun Clauses as Objects of Prepositions
- That-Clauses in Detail
- Wh-Clauses (Embedded Questions)
- If/Whether Clauses
- Noun Clauses vs. Other Dependent Clauses
- Practice Exercises
What Is a Noun Clause?
A noun clause is a dependent (subordinate) clause that performs the function of a noun. It contains a subject and a verb but cannot stand alone as a sentence. Instead, it functions as a single unit within a larger sentence, filling any role that a noun can fill.
Simple noun: "I know the answer."
Noun clause: "I know what the answer is."
In both sentences, the bold portion serves as the direct object of "know." The noun clause "what the answer is" functions exactly like the noun "the answer"—it answers the question "What do I know?"
Key Characteristics
- Contains a subject and a verb
- Cannot stand alone as a complete sentence
- Functions as a noun (subject, object, complement, or object of a preposition)
- Usually begins with a specific set of introductory words
- Can be replaced by a pronoun (it, something, this) to test identification
Words That Begin Noun Clauses
Noun clauses are introduced by the following types of words:
| Category | Words | Example |
|---|---|---|
| That | that | "I believe that she is honest." |
| Wh-words | what, who, whom, which, whose | "I wonder who called." |
| Wh-adverbs | when, where, why, how | "She explained how it works." |
| If/Whether | if, whether | "I don't know whether he's coming." |
| -ever words | whatever, whoever, whichever, wherever, whenever, however | "Whoever arrives first wins." |
Noun Clauses as Subjects
A noun clause can serve as the subject of a sentence, taking the place where a regular noun would go:
"What she said surprised everyone." (What surprised everyone? → What she said.)
"That he passed the exam was great news."
"Whether we should go remains undecided."
"How they escaped is a mystery."
"Whoever finishes first gets a prize."
When a noun clause serves as the subject, the verb of the main clause must agree with the clause as a whole (treated as singular): "What we need is more time" (not "are").
Using "It" as a Placeholder
English often uses "it" as a placeholder subject, moving the noun clause to the end for smoother readability:
Noun clause first: "That she won was exciting."
With "it": "It was exciting that she won."
Both forms are correct, but the "it" construction is more common in everyday English because it avoids a long subject before the verb.
Noun Clauses as Direct Objects
The most common function of noun clauses is as direct objects of verbs like know, believe, think, say, tell, realize, understand, hope, wish, doubt, discover, notice, remember, forget:
"I believe that the project will succeed."
"She knows where the keys are."
"We discovered what had gone wrong."
"He asked whether I could help."
"They remember how difficult it was."
Noun Clauses as Indirect Objects
Less commonly, noun clauses can function as indirect objects:
"Give whoever answers the door the package." (Give the package to whom? → Whoever answers the door.)
"She teaches whoever wants to learn the basics." (Teaches the basics to whom?)
Noun Clauses as Subject Complements
A noun clause can follow a linking verb and rename or describe the subject:
"The problem is that we have no budget."
"The question is whether we should proceed."
"My concern is how this will affect the team."
"Home is wherever you feel most comfortable."
Noun Clauses as Objects of Prepositions
Noun clauses can serve as the objects of prepositions:
"I'm interested in what you have to say."
"She was worried about whether the flight would be delayed."
"The prize goes to whoever scores the highest."
"We argued over who should lead the project."
That-Clauses in Detail
Clauses beginning with "that" are the most common type of noun clause. The word "that" in these clauses is a subordinating conjunction (not a pronoun)—it introduces the clause but doesn't play a grammatical role within it.
Omitting "That"
When a that-clause functions as a direct object, "that" can often be omitted without changing the meaning:
"I think (that) she's right." — Both forms are correct.
"He said (that) he would come." — "That" is optional.
However, "that" should generally be kept when:
- The clause is the subject: "That he lied is obvious." (Omitting "that" causes confusion.)
- There are multiple clauses: "She said that the plan was ready and that we could start."
- The clause is separated from the verb: "He promised his team that things would improve."
Wh-Clauses (Embedded Questions)
When question words (who, what, where, when, why, how, which, whose) introduce noun clauses, they create embedded questions. A crucial point: embedded questions use statement word order, not question word order.
Direct question: "Where does she live?" (question word order)
Embedded question: "I know where she lives." (statement word order)
Direct question: "What is his name?"
Embedded question: "Tell me what his name is."
Common Error: Don't use question word order in embedded questions. Say "I wonder where he is" (not "I wonder where is he"). Say "She asked what time it was" (not "She asked what time was it").
If/Whether Clauses
"If" and "whether" introduce noun clauses derived from yes/no questions:
Yes/no question: "Will they come?"
Noun clause: "I don't know if they will come." / "I don't know whether they will come."
Both "if" and "whether" work in most contexts, but "whether" is preferred:
- As a subject: "Whether we go depends on the weather." (Not "If we go depends...")
- After prepositions: "The decision about whether to proceed..." (Not "about if...")
- With "or not" directly following: "Whether or not you agree..." (Not "if or not...")
Noun Clauses vs. Other Dependent Clauses
| Clause Type | Function | Example |
|---|---|---|
| Noun clause | Functions as a noun | "I know that she left." (object) |
| Adjective clause | Modifies a noun | "The woman who left was my sister." (modifies "woman") |
| Adverb clause | Modifies a verb/clause | "She left because she was tired." (modifies "left") |
The substitution test helps distinguish them: if you can replace the clause with a pronoun (it, something), it's a noun clause. If you can replace it with an adjective or an adverb, it's an adjective or adverb clause respectively.
Practice Exercises
Identify the noun clause in each sentence and state its function:
- "What she discovered changed everything."
- "The teacher explained how photosynthesis works."
- "The truth is that nobody really knows."
- "I'm curious about what happened next."
- "Whether the plan succeeds depends on funding."
- "Give whoever calls first the appointment."
Answers: 1. "What she discovered" — subject. 2. "how photosynthesis works" — direct object. 3. "that nobody really knows" — subject complement. 4. "what happened next" — object of preposition "about." 5. "Whether the plan succeeds" — subject. 6. "whoever calls first" — indirect object.
Key Takeaway: Noun clauses are dependent clauses that function like nouns—as subjects, objects, complements, or objects of prepositions. They begin with words like "that," "what," "who," "whether," "how," and other wh-words. Mastering noun clauses allows you to express complex ideas, embed questions, and report speech with precision.