English clauses are commonly divided into two main types: independent clauses and dependent clauses. Dependent clauses can be classified further as noun clauses, relative (adjective) clauses, and adverbial clauses, depending on their function.
These categories aren’t all at the same level. A clause can have more than one classification because each label describes a different feature.
For example:
Because the road was closed, the bus arrived late.
Because the road was closed is a dependent clause. It is also adverbial because it explains the reason for the delay, finite because it contains the past-tense verb was, and declarative in grammatical form.
Each label tells us something different about the clause.
How Are Clauses Classified in English Grammar?
English clauses can be classified in several ways. Four particularly useful distinctions concern grammatical independence, function, form, and verb structure.
| Classification | Main types or examples | What it describes |
|---|---|---|
| Grammatical independence | Independent, dependent | Whether the clause can stand alone as a sentence |
| Grammatical function | Noun, relative, adverbial | What a subordinate clause does |
| Grammatical form | Declarative, interrogative, imperative, exclamative | How the clause is structured |
| Verb structure | Finite, non-finite | Whether the clause contains a finite verb phrase |
The noun, relative, and adverbial categories are the three familiar functional groups in traditional school grammar. They are useful, but they do not represent every distinction made in more detailed grammatical descriptions.
Independent and Dependent Clauses
The first distinction is whether a clause can stand alone as a sentence.
Independent Clauses
An independent clause, also called a main clause, can form a complete sentence.
The ferry reached the harbour before sunset.
The subject is the ferry, and the finite verb is reached.
Two independent clauses can also be joined:
The ferry reached the harbour, but the passengers remained on board.
Both clauses can stand alone. The conjunction but connects them without making either grammatically dependent on the other.
Dependent Clauses
A dependent clause, also called a subordinate clause, functions within a larger grammatical structure.
although the final inspection was incomplete
This clause introduces a concession but cannot normally stand alone as a complete sentence.
It can be combined with a main clause:
The gallery opened to visitors although the final inspection was incomplete.
Not every dependent clause sounds like an unfinished idea, however.
The receptionist confirmed that the parcel had arrived.
The clause that the parcel had arrived expresses an understandable idea. Grammatically, it supplies the content of what the receptionist confirmed.
Three Main Types of Dependent Clauses
In traditional school grammar, dependent clauses are commonly grouped into three functional categories: noun clauses, relative (adjective) clauses, and adverbial clauses.
The difference lies in what each clause does within a sentence.
1. Noun Clauses
A noun clause can function as the subject of a sentence or as the complement of a verb, adjective, or preposition.
Consider:
Whether the old cinema will reopen remains uncertain.
The clause whether the old cinema will reopen functions as the subject.
A noun phrase can occupy the same grammatical position:
The reopening remains uncertain.
The meaning isn’t exactly the same, but both occupy the subject position.
Noun clauses also appear after verbs:
The caretaker discovered that someone had left a window open.
The bold clause tells us what the caretaker discovered.
Traditional school grammar commonly calls these noun clauses. More detailed grammatical descriptions may distinguish declarative content clauses from embedded interrogative clauses.
2. Relative (Adjective) Clauses
A relative clause typically modifies a noun or noun phrase by identifying or describing a person or thing.
The musician who composed the opening piece attended the concert.
The bold clause identifies the musician being discussed.
In traditional grammar, relative clauses are often called adjective clauses because they perform a descriptive or identifying function.
Some relative clauses help identify exactly which person or thing is meant. Others provide additional information about someone or something already identified.
An object relative pronoun can also be omitted in certain defining relative clauses:
The photographs we found in the attic were badly faded.
The bold clause modifies photographs. We could also write that we found in the attic.
3. Adverbial Clauses
An adverbial clause expresses a relationship such as time, reason, condition, purpose, or concession.
The organisers moved the concert indoors because the weather forecast had changed.
The bold clause explains why the concert was moved.
Compare:
If the replacement arrives by Friday, the repairs can begin on Monday.
This clause introduces a condition rather than a reason for something that has already happened.
Adverbial clauses can be classified further according to the relationship they express.
| Type | Example | Relationship |
|---|---|---|
| Time | We closed the shutters when the storm reached the coast. | When something happened |
| Reason | David stayed behind because his luggage was missing. | Why something happened |
| Condition | Unless the documents arrive today, approval will be delayed. | What must happen or be true |
| Purpose | The speakers used microphones so that everyone could hear. | Intended result |
| Concession | Although the path was steep, the group reached the summit. | An outcome despite a contrasting circumstance |
| Place | Put the spare chairs where visitors can reach them. | Location |
These are subtypes of adverbial clauses, not additional broad categories alongside independent and dependent clauses.
Concession describes a situation in which something happens despite circumstances that might suggest a different outcome.
How to Tell Which Type of Dependent Clause You Have
A clause’s opening word does not always reveal its type. What matters is how the clause functions within the larger sentence.
Consider three examples.
The manager couldn’t explain why the screen went blank.
The bold clause provides the content of what the manager couldn’t explain. It is a noun clause, more specifically an embedded interrogative content clause.
The technician left because the repair was complete.
This clause gives the reason for the technician’s departure. It is an adverbial clause.
The monitor that stopped working yesterday needs replacing.
Here, the relative clause identifies the monitor. It modifies the noun monitor.
Although all three are dependent clauses, their functions differ.
| Question to consider | Likely classification |
|---|---|
| Does it function as a subject or provide the content of something said, known, asked, or believed? | Noun/content clause |
| Does it modify or identify a noun or noun phrase? | Relative clause |
| Does it express time, reason, condition, concession, or another circumstance? | Adverbial clause |
These questions help with common constructions, although they do not cover every possible subordinate clause.
Why the Opening Word Can Be Misleading
The word when is a good example.
Adverbial clause
When the train departed, the platform grew quiet.
When the train departed tells us when the platform grew quiet.
Noun clause
The dispatcher couldn’t confirm when the train departed.
Here, when the train departed is an embedded interrogative content clause. It represents the unresolved question of the departure time and functions as the complement of confirm.
It does not tell us when the dispatcher was unable to confirm something.
Relative clause
The morning when the train departed was unusually cold.
In this sentence, when the train departed modifies morning, identifying the morning being described.
The opening word is the same, but the grammatical function changes with the sentence.
Clause Types by Grammatical Form
Clauses can also be classified by grammatical form. Four familiar types are declarative, interrogative, imperative, and exclamative.
These forms are commonly associated with statements, questions, instructions, and exclamations. However, grammatical structure and communicative purpose do not always match exactly.
Declarative Clauses
Declarative clauses typically place the subject before the verb and are commonly used to make statements.
The rehearsal begins at six.
They can also be negative:
The rehearsal does not include the final scene.
Written declarative sentences usually end with periods, but punctuation alone does not determine grammatical form.
Interrogative Clauses
Interrogative clauses have structures associated with questions.
Has the delivery been confirmed?
Here, the auxiliary verb has appears before the subject the delivery.
Other interrogative clauses begin with question words:
Why did the committee postpone the announcement?
An interrogative clause can also appear inside a declarative sentence:
Nobody knew whether the tickets were still available.
The subordinate clause whether the tickets were still available is interrogative in form, although the complete sentence is declarative.
Imperative Clauses
Imperative clauses are commonly used for instructions, commands, requests, or invitations.
Keep the entrance clear.
The subject you is understood rather than written.
An imperative can also be polite:
Please return the equipment before leaving.
Both examples have imperative grammatical form, regardless of their tone.
Exclamative Clauses
Exclamative clauses have characteristic structures often beginning with what or how.
What a remarkable view this is!
How quickly the weather changed!
These constructions express a strong reaction.
An exclamation mark, however, does not automatically make a clause exclamative in grammatical form.
I never expected that result!
This is declarative in form, even though the punctuation conveys surprise.
Finite and Non-Finite Clauses
Another distinction concerns the verb structure within a clause.
A finite clause contains a finite verb phrase, which carries grammatical information such as tense or mood.
The volunteers repaired the footbridge.
The verb repaired is finite and expresses past tense.
Finite clauses may be independent or subordinate.
The volunteers stopped working when darkness fell.
Both the volunteers stopped working and when darkness fell are finite clauses.
A non-finite clause contains a non-finite verb form that does not independently express tense.
To avoid further delays, the contractor ordered the materials early.
The opening construction to avoid further delays expresses purpose. Its understood subject is the contractor.
But the understood subject of a non-finite clause is not always the subject of the main clause.
The manager asked Priya to check the figures.
Here, to check the figures is a non-finite complement clause, and Priya is understood to be the person checking the figures.
Non-finite constructions can also use participles:
Exhausted by the journey, Marcus went straight to bed.
The opening participial construction provides background information about Marcus.
Modern grammatical descriptions can treat these constructions as non-finite clauses. Traditional classroom grammar often calls them infinitive or participial phrases.
Some descriptions also recognize verbless constructions, such as if necessary, as elliptical or verbless clauses. This is a more advanced distinction and is not normally part of the basic school-grammar classification.
How Different Clause Types Work in One Sentence
A clause can be subordinate to another clause, and that larger clause may contain a further subordinate clause.
Consider:
The person who called yesterday said that the venue would be closed if heavy rain continued.
The sentence contains four finite clauses, but they are not four separate statements placed side by side.
The complete main clause is:
The person who called yesterday said that the venue would be closed if heavy rain continued.
Within it, three subordinate clauses perform different functions.
The Relative Clause
who called yesterday
This clause modifies person, identifying who made the statement.
It belongs inside the subject noun phrase the person who called yesterday.
The Noun (Content) Clause
that the venue would be closed if heavy rain continued
This clause tells us what the person said.
It functions as the complement of said.
The Adverbial Clause
if heavy rain continued
This conditional clause expresses the circumstance under which the venue would be closed.
It is contained within the larger content clause.
The nesting can be represented as follows:
Main clause: The person who called yesterday said that the venue would be closed if heavy rain continued.
- Inside the subject: who called yesterday — relative clause.
- Complement of said:that the venue would be closed if heavy rain continued — noun/content clause.
- Inside that content clause: if heavy rain continued — conditional adverbial clause.
The three subordinate clauses are all dependent and finite, but they perform different grammatical functions. Their relationships explain how the sentence fits together.
Check Your Understanding
Try classifying the bold clauses before reading the explanations.
1. Noun Clause or Adverbial Clause?
The guide explained why the northern entrance was closed.
Answer: A dependent noun clause, more specifically an embedded interrogative content clause.
It supplies the content of the guide’s explanation.
The word why suggests a reason, but the clause is not an adverbial clause explaining why the guide spoke. It tells us what the guide explained.
2. Relative Clause or Adverbial Clause?
The evening when the power returned brought relief to the residents.
Answer: A dependent relative clause.
The clause modifies evening, identifying which evening brought relief.
Compare:
When the power returned, the residents cheered.
Here, the same introductory word begins an adverbial time clause, indicating when the cheering happened.
3. What Classifications Apply to This Clause?
Although the instructions were unclear, Priya assembled the shelf correctly.
Answer: Although the instructions were unclear is a dependent adverbial clause of concession.
It is dependent because it functions within the larger sentence. It is adverbial because it expresses an unexpected contrast: Priya assembled the shelf correctly despite the unclear instructions.
It is also finite, with were as its past-tense verb.
These labels describe different grammatical features of the same clause.
4. Can a Sentence Contain Clauses of Different Grammatical Forms?
Have the organisers confirmed that the event is outdoors?
Answer: Yes.
The main clause is interrogative in form:
Have the organisers confirmed that the event is outdoors?
It contains a subordinate declarative content clause:
that the event is outdoors
The whole sentence is a question, but the embedded clause has declarative structure. The sentence’s overall form does not determine the form of every clause within it.
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