Advanced … min read · Updated 2026-06-20

Complex Sentences: Noun Clauses

Good academic writing mixes sentence types. A complex sentence has one independent clause and one or more dependent clauses. The first kind of dependent clause is the noun clause — a clause that does the job of a noun. There are three types: that-clauses, wh-word clauses, and if/whether clauses.

That-clauses are introduced by that (often omitted). They frequently follow reporting verbs used for citations: Greene (2016) points out that class size is a key factor. In academic writing they often appear in the passive with "it": It is generally agreed that…, It has been shown that…

Certain verbs and adjectives are followed by a base-form verb in the that-clause (the subjunctive): advise, demand, insist, propose, recommend, suggest, urge; and essential, necessary, important, vital. Example: It is necessary that governments reduce reliance on fossil fuels (not reduces); It is recommended that greater precautions be taken.

Wh-word clauses come from wh-questions but use statement word order (subject + verb, no do/does/did): It is not known where the epicentre was (not where was the epicentre).

If/whether clauses come from yes/no questions. Whether is more formal than if and more common in academic writing: The results determined whether the drug entered trials.

Tip: After verbs and adjectives like recommend, suggest, essential, necessary, use the base form of the verb in the that-clause: It is essential that he be present — not is present.

Common mistake: Keeping question word order in a wh- or if-clause ("It is unclear where does the substance originate"). Use statement order: where the substance originates.

✏️ Test Yourself

1. A clause that functions as a noun is a ___ clause.

2. <em>That, wh-,</em> and <em>if/whether</em> are the three types of ___ clause.

3. "It is recommended that he ___ present."

4. Which is more formal in academic writing, <em>if</em> or <em>whether</em>?

📒 Words to learn

Oasis (n)

MeaningA shelter serving as a place of safety or sanctuary.

Synonyms: Haven, Refuge

The park was an oasis of calm in the middle of the busy city.

Prodigious (adj)

MeaningSo great in size or force as to elicit awe.

Synonyms: Enormous, Colossal

The prodigious effort of the team resulted in a successful project.

Barrage (n)

MeaningHeavy fire or overwhelming outpouring of something.

Synonyms: Bombardment, Onslaught

The reporter faced a barrage of questions from the press.

Subsequent (adj)

MeaningFollowing in time or order.

Synonyms: Following, Later

The flood and its subsequent damage affected the entire town.

Outbreak (n)

MeaningA sudden violent spontaneous occurrence.

Synonyms: Eruption, Explosion

The outbreak of a new virus caused widespread panic.

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