Sentence Structure and Clauses

Lesson 3: Noun Clauses

Lesson: 3 of 9 | Level: 🟠 Intermediate — 🟣 Upper-Intermediate

1. Lesson Overview

A noun clause is a subordinate clause that functions in exactly the same grammatical positions as a noun — as the subject, object, complement, or object of a preposition within a sentence. Unlike adverbial clauses — which modify verbs and whole clauses — and relative clauses — which modify nouns — noun clauses occupy the core positions of sentence structure, replacing single nouns or noun phrases with entire clauses.

Noun clauses are one of the most important and most productive structures in advanced English. They appear constantly in academic writing, in reported speech, in formal argument, and in any context where complex ideas need to be expressed precisely within a single sentence structure. Mastering them — understanding how they are formed, what positions they occupy, and what words introduce them — is essential for writing at advanced level.

Objectives

By the end of this lesson, you will be able to:

• Identify and form noun clauses introduced by that, whether/if, and question words
• Use noun clauses correctly as subjects, objects, complements, and objects of prepositions
• Apply the subjunctive in formal that-clauses after verbs of recommendation and requirement
• Use it as a dummy subject to introduce noun clauses in subject position
• Recognise and correct common errors in noun clause formation and use

2. Core Content

A. What Is a Noun Clause?

A noun clause is a subordinate clause that performs the grammatical function of a noun. Just as a noun or noun phrase can be the subject, object, or complement of a sentence, a noun clause can occupy exactly the same positions.

Compare the following:

The discovery surprised the scientific community. (noun phrase as subject) That the species could survive at 400°C surprised the scientific community. (noun clause as subject)

Scientists confirmed the finding. (noun phrase as object) Scientists confirmed that the species had never previously been observed. (noun clause as object)

In both cases, the noun clause occupies the same grammatical position as the noun phrase it replaces — but it carries far more information, because it contains its own subject and finite verb.

B. Words That Introduce Noun Clauses

Noun clauses are introduced by three types of connector:

1. That

That-clauses are the most common type of noun clause. They are introduced by the subordinating conjunction that and express a fact, belief, or proposition.

For example:

It is widely accepted that the deep ocean plays a significant role in regulating global climate. Scientists have demonstrated that hydrothermal vent communities depend entirely on chemosynthesis.

That can often be omitted in informal contexts when the noun clause functions as an object — but it is retained in formal and academic writing.

Scientists believe that the findings are significant. (formal — that retained) Scientists believe the findings are significant. (informal — that omitted)

2. Whether and if

Whether-clauses and if-clauses are introduced by whether or if and express an indirect question — the content of a yes/no question functioning as a noun.

For example:

Whether the species can survive at greater depths remains unknown. The committee has not yet decided whether to proceed with the next phase. Scientists are investigating whether the anomaly was caused by instrument error.

Whether is strongly preferred over if in formal and academic writing, and whether is required in subject position, after prepositions, and in the whether or not construction.

3. Question words — Wh- words

Question word clauses are introduced by who, what, where, when, why, which, how, how much, how many, how long, and similar expressions. They express the content of an indirect wh- question — functioning as a noun.

For example:

What scientists have discovered in the deep ocean continues to astonish the world. The team explained how the vent ecosystem functioned without sunlight. Nobody knows why the species disappeared so suddenly from the monitoring record.

C. The Grammatical Positions of Noun Clauses

1. Noun clause as subject

A noun clause can function as the subject of a sentence — taking the place of a noun phrase in subject position.

For example:

That the deep ocean remains largely unexplored is one of the most remarkable facts about our planet. Whether the species has developed resistance to elevated temperatures remains to be determined. How the vent ecosystem generates and distributes energy is not yet fully understood.

When a noun clause functions as subject, it is often replaced by the dummy subject it — placing the noun clause at the end of the sentence, where it is easier to process. This is extremely common in English and is examined in detail in section D below.

2. Noun clause as object

A noun clause most commonly functions as the object of a transitive verb — the direct object position.

For example:

Scientists have confirmed that the new species belongs to a previously undescribed genus. The researcher demonstrated how the organism produced bioluminescent light. The committee decided whether the expedition should be extended. Nobody knows what causes the periodic intensification of activity at the vent field.

3. Noun clause as subject complement

A noun clause can function as a subject complement — following a linking verb and describing or identifying the subject.

For example:

The most significant finding is that the species can survive without any access to sunlight. The real question is whether the regulatory framework is adequate to protect these ecosystems. The conclusion was that the data supported the original hypothesis.

4. Noun clause as object complement

Less commonly, a noun clause can function as an object complement — following the direct object and saying something about it.

For example:

The committee considered what the researcher had found to be extraordinary.

5. Noun clause as object of a preposition

A noun clause can follow a preposition — functioning as the object of a preposition. In this position, whether is required — if is not used.

For example:

The debate centres on whether deep-sea mining can be conducted without causing lasting damage. There is considerable uncertainty about how long the species can survive under these conditions. Scientists disagree about what caused the sudden decline in population at the monitoring site.

Note that that-clauses do not normally follow prepositions directly — they require an intervening the fact that construction.

There is growing evidence for the fact that vent ecosystems are under increasing threat. ✅ There is growing evidence that vent ecosystems are under increasing threat. ✅ (more natural — for the fact that often avoided by restructuring)

D. It as a Dummy Subject — Extraposition

When a noun clause functions as the subject of a sentence, English speakers and writers very commonly use the dummy subject it in the actual subject position — moving the noun clause to the end of the sentence, where longer and more complex elements are more naturally placed. This process is called extraposition.

Compare:

That the deep ocean is poorly understood is remarkable. (noun clause as subject — grammatically correct but heavy) It is remarkable that the deep ocean is poorly understood. (extraposition — it as dummy subject — more natural)

Whether the species can survive at greater depths remains unknown. (grammatically correct) It remains unknown whether the species can survive at greater depths. (extraposed — more natural)

Extraposition with it is extremely common in English — particularly in academic and formal writing, where complex noun clauses as subjects would create very front-heavy sentences.

Common it + adjective + that-clause patterns

E. The Subjunctive in That-Clauses

In formal and academic English, certain verbs and adjectives are followed by that-clauses in which the subjunctive mood is used — the base form of the verb, unchanged for person or tense. This construction is used after verbs and adjectives expressing recommendation, requirement, suggestion, demand, and importance.

Verbs followed by subjunctive that-clauses

recommend, suggest, propose, demand, require, request, insist, urge, advocate, ask, stipulate, prefer

For example:

The committee recommended that the expedition should be extended by two weeks. (with should — common in British English) The committee recommended that the expedition be extended by two weeks. (bare subjunctive — formal, used in both British and American English) The funding body required that all data be archived within thirty days. (bare subjunctive) The expert urged that immediate action be taken to protect the vent field.

Adjectives followed by subjunctive that-clauses

essential, vital, important, necessary, critical, imperative, advisable, desirable

For example:

It is essential that all instruments be calibrated before each dive. It is vital that the findings be independently verified before publication. It is imperative that a comprehensive baseline survey be conducted before operations begin.

Note the distinction between British and American usage — American English strongly prefers the bare subjunctive (be, have, include, proceed); British English commonly uses should + bare infinitive as an alternative (should be, should have, should include). Both are acceptable in formal writing — the should form is more common in British academic prose.

F. Sequence of Tenses in Noun Clauses

When a noun clause follows a past-tense reporting verb or main verb, the tense of the noun clause typically shifts back — following the same backshift rules established in Module 7.

For example:

Scientists believe that the ecosystem is unique. (present reporting verb — no backshift) Scientists believed that the ecosystem was unique. (past reporting verb — backshift: is → was) The team discovered that a new species had colonised the site. (past main verb — had colonised for earlier event)

When the noun clause expresses a permanent fact or general truth, the present tense is retained even with a past main verb — as established in Module 7, Lesson 6.

Scientists confirmed that vent ecosystems depend on chemosynthesis. (permanent fact — present tense retained)

3. Usage in Context

• Use that-clauses as objects after verbs of belief, knowledge, assertion, and demonstration — the most common position for noun clauses in academic writing.

Scientists have confirmed that hydrothermal vent communities represent some of the most biodiverse ecosystems on the planet. The study demonstrates that the rate of ocean acidification is accelerating in direct response to rising atmospheric carbon dioxide.

• Use that-clauses as subjects with extraposition — it + adjective/verb + that-clause — for a more natural and readable sentence structure.

It is now well established that deep-sea vent communities can sustain complex food webs in the complete absence of sunlight. It is important to note that the sample size of the current study is relatively small and that the findings may not be fully representative.

• Use whether-clauses for indirect yes/no questions — in subject position, after prepositions, and as objects of verbs of uncertainty and investigation.

Whether the species can survive at greater depths is a question that future expeditions will need to address. Scientists are investigating whether the anomalous readings indicate a previously undetected vent field. The debate about whether deep-sea mining can be conducted sustainably is far from resolved.

• Use question word clauses as objects after verbs of explaining, showing, knowing, and understanding.

The team explained how the bioluminescent mechanism operated at the cellular level. Nobody fully understands why certain vent species are found at only one site while others are distributed across multiple ocean basins. The research reveals what happens to ecosystems when the flow of hydrothermal fluid is interrupted.

• Use what-clauses as subjects — what functions as both the subject of the noun clause and the connector.

What scientists have discovered in the deep ocean over the past four decades has transformed our understanding of life on Earth. What the data shows is far more complex than the original hypothesis had predicted.

• Use how + adjective/adverb + clause structures to express degree and extent as noun clauses.

Scientists have only recently begun to appreciate how complex the food webs of hydrothermal vent ecosystems really are. The survey revealed how rapidly the population had declined since baseline measurements were first taken.

• Apply the subjunctive — or should + bare infinitive in British English — after verbs and adjectives expressing recommendation, requirement, and necessity.

The panel recommended that a comprehensive environmental impact assessment be conducted before any further operations are authorised. It is essential that all monitoring instruments be calibrated and tested before the expedition departs.

• Use it is worth + gerund + that-clause constructions to introduce qualifications and caveats in academic writing.

It is worth emphasising that the findings of this study are preliminary and that further investigation is required before firm conclusions can be drawn. It is worth noting that the methodology used here differs in several important respects from that employed in earlier studies.

• Use the fact that to introduce a noun clause after a preposition — that-clauses cannot follow prepositions directly.

There is compelling evidence for the fact that deep-sea ecosystems are under increasing pressure from warming, acidification, and physical disturbance. The committee expressed concern about the fact that baseline measurements had not been established before the operations began.

• In academic writing, noun clauses in subject position with extraposition allow writers to build complex, qualified claims while maintaining a readable sentence structure.

It has been proposed that the current regulatory framework for deep-sea mining is inadequate — a proposal that has attracted considerable attention and some controversy in the scientific community.

• Use whoever, whatever, wherever, whenever, however — free relatives — as noun clauses with an indefinite, generalising meaning.

Whoever conducts the next expedition will have access to the most comprehensive baseline data ever assembled for this region. Whatever the findings reveal, they will contribute significantly to our understanding of deep-sea ecology. The team recorded whatever conditions prevailed at each site, regardless of whether they fell within the expected range.

4. Common Errors and Corrections

5. Lesson Mastery

After completing this lesson, you should now be able to:

    ✅ Identify and form noun clauses introduced by that, whether/if, and question words

    ✅ Use noun clauses correctly as subjects, objects, complements, and objects of prepositions

    ✅ Apply the subjunctive in formal that-clauses after verbs of recommendation and requirement

    ✅ Use it as a dummy subject to introduce noun clauses in subject position

    ✅ Recognise and correct common errors in noun clause formation and use