A clause is a grammatical unit typically built around a verb. Many clauses contain an explicit subject and verb: She laughed. An independent clause can form a complete sentence; a dependent or subordinate clause functions within a larger sentence: because she was happy. Commands and non-finite clauses need a little extra care because their subject may be understood.
Start with the examples below, then try 12 clause exercises with explained answers. The guide covers identification, sentence joining and punctuation, including why What she said surprised me has no comma after said.
The Core Concept: What Is a Clause in Grammar?
Compare I stayed home. I was tired. with I stayed home because I was tired. Both versions are grammatical. The second explicitly connects the decision with its reason. Clause teaching is about making that relationship clear, not making every sentence longer.
Finding the subject and verb is a useful first check for ordinary finite clauses. She laughed has the subject she and the past-tense verb laughed. Because he forgot also contains a subject and verb, but needs a main clause in a complete formal sentence. Other elements may be necessary too: She put has a subject and verb, but this use of put needs an object and a location, as in She put the keys on the desk.
| Example | What it is | What to notice |
|---|---|---|
| The class ended. | Independent finite clause | Subject the class; past-tense verb ended. |
| when the class ended | Dependent finite clause | It provides a time within a larger sentence. |
| after the class | Prepositional phrase | Here the class is a noun phrase; there is no verb. |
| Close the door. | Independent imperative clause | The listener, you, is understood as the subject. |
| to finish on time in To finish on time, we need help. | Non-finite clause of purpose | To finish does not mark tense; its understood subject is we. |
A phrase can contain a verb too: has been waiting is a verb phrase within Leo has been waiting. So “contains a verb” alone is not a complete test. This guide starts with finite clauses, then includes the imperative and non-finite exceptions. See Cambridge's explanations of clause structure, imperatives and finite and non-finite clauses.
Independent and Dependent Clauses
The bus arrived. can stand as a sentence. Because the bus arrived supplies a reason within a sentence such as We stopped waiting because the bus arrived. “Dependent” and “subordinate” describe the same broad relationship here; they are not two separate levels of difficulty.
| Sentence | Main clause | Dependent clause and its job |
|---|---|---|
| She stayed home because she felt sick. | She stayed home | because she felt sick: reason |
| I called her when I got home. | I called her | when I got home: time |
| They bought the book that you recommended. | They bought the book that you recommended | that you recommended: identifies book, inside the main clause's object |
The third example shows that clauses can be nested. A subordinate clause need not sit neatly before or after the rest of the sentence. Words such as because, when, if and who are useful clues, but inspect the whole sentence: Who called? is an independent question.
In formal connected writing, Because I was late. is normally a fragment if it stands alone. Attach a result: Because I was late, I missed the introduction. In conversation, the same fragment can be a natural answer to “Why did you miss the introduction?” Purpose and context matter.
Noun, Relative and Adverbial Clauses
These familiar classroom labels describe the job a subordinate clause does. They are useful for teaching, although advanced grammars may group and name some structures differently.
Noun clauses: subjects and complements
A clause can occupy a position often filled by a noun phrase. Compare What she wrote was clear with Her message was clear. In each sentence, the bold part is the subject. Other examples include I know where she lives and The problem is that we started late. Traditional school grammar often calls all of these noun clauses; what she wrote is also analysed as a fused or free relative construction.
Relative clauses: information about a noun
In The man who lives next door is a doctor, the relative clause identifies man. In I lost the phone that my sister gave me, it identifies phone. A useful contrast is I know that she left, where the clause supplies the content of what is known, and the book that she bought, where the clause describes a noun.
- Defining/restrictive: The book that I borrowed is overdue. The clause helps identify which book; do not put commas around it.
- Non-defining/nonrestrictive: This book, which I borrowed, is overdue. The book is already identified; the clause adds information and takes commas.
For things, both that and which can introduce a defining relative clause, although some style guides prefer that. Use which, not that, for a non-defining relative clause about a thing. An object relative pronoun can sometimes be omitted: the book I borrowed. A subject relative pronoun cannot be omitted in the man who lives next door. The British Council has further examples of defining and non-defining relative clauses.
For extra information inserted into a sentence, use the parenthetical punctuation examples and practice to compare paired commas, dashes and parentheses. Check whether the information identifies the person or thing before treating it as an aside.
Adverbial clauses: time, reason, condition and contrast
- Time: We left after the film ended.
- Reason: She stayed home because she felt sick.
- Condition: If you arrive early, please wait outside.
- Contrast: Although it was raining, we went out.
The conjunction carries meaning. She was tired, but she finished her homework presents a contrast. Changing it to She finished her homework because she was tired invents a causal relationship unless the context supports that reason. For conditional patterns, try the separate conditionals exercises.
Punctuation Rules That Depend on the Clause's Job
1. Put a comma after an introductory adverbial clause
Because it was raining, we stayed inside. When the same reason clause follows the main clause, it normally needs no comma: We stayed inside because it was raining.
Do not turn this into “every dependent clause at the beginning needs a comma.” In What she said surprised me, the opening construction is the subject of surprised. A comma after said would separate the subject from its predicate. The same applies to That the door was unlocked worried us. Compare Purdue's guidance on introductory elements and subjects.
2. Use commas for additional relative information
Our only printer, which is upstairs, needs paper. Both commas belong to the added clause. By contrast, The printer that is upstairs needs paper selects that printer from others. Removing a clause may leave grammatical English while changing which person or thing is meant; grammatical completeness alone is not the test.
3. Join independent clauses with suitable punctuation
- Comma and coordinating conjunction: I wanted to go, but I was too tired.
- Semicolon: She finished the task; she sent the email.
- Full stop: She finished the task. She sent the email.
I wanted to go, I was too tired is a comma splice; I wanted to go I was too tired is a fused sentence. However is not a coordinating conjunction: write I wanted to go; however, I was too tired or start a new sentence with However,. These are standard formal-writing patterns; see Purdue's comma rules and our sentence structure guide.
Extension: words understood from context
In She reads more than I do, do stands for the repeated action read. In He is taller than I am, the comparison leaves part of the meaning understood. These examples are useful after learners can identify the full structures: an analysis must account for understood material as well as the words visible on the page.
12 Clause Exercises with Answers
Write an answer before opening each explanation. Questions 1–5 identify structure; 6–10 test punctuation; 11–12 join ideas. These are original practice examples, not a proficiency test.
Printed copies include writing spaces. Answers remain available below on screen.
Identify the structure
In We waited because the train was late, copy the main clause and the dependent clause. What relationship does the dependent clause express?
Answer 1 and explanation
Main: We waited. Dependent: because the train was late. It gives the reason for waiting; the train is its subject and was its verb.
Which is a finite clause: A after the lesson or B after the lesson ended? Identify its subject and verb.
Answer 2 and explanation
B. The lesson is the subject and ended is the past-tense verb. A is a prepositional phrase; it has no verb.
In To catch the early bus, Lena set an alarm, is to catch the early bus a finite or non-finite clause? Who is meant to catch the bus?
Answer 3 and explanation
It is non-finite: the infinitive to catch does not show tense. Lena is its understood subject. The clause gives her purpose in setting the alarm.
A notice says Please close the gate. Is this an incomplete fragment because no subject is written? Explain.
Answer 4 and explanation
No. It is a complete imperative clause. The person reading the instruction, you, is understood as the subject. An explicit subject is not required here.
Compare A I heard that the concert was cancelled and B The concert that we booked was cancelled. Which that-clause gives the content of a report, and which identifies a noun?
Answer 5 and explanation
A: that the concert was cancelled is a content clause, traditionally a noun clause, giving what was heard. B: that we booked is a relative clause identifying concert. The first word alone does not decide a clause's function.
Choose punctuation from the meaning
Add the comma needed in standard formal writing: When the visitors arrive please show them the workshop.
Answer 6 and explanation
When the visitors arrive, please show them the workshop. The initial adverbial clause sets the time for the main imperative clause. Put the comma after arrive.
A learner wrote What the visitors requested, surprised the organiser. Remove the unnecessary comma and explain why it is wrong.
Answer 7 and explanation
What the visitors requested surprised the organiser. What the visitors requested is the subject of surprised; it is not an introductory time or reason clause. Do not separate it from its predicate with a comma.
Only three of ten members borrowed tools. The instruction applies only to those three. Should this sentence have commas around the relative clause? Members who borrowed tools must return them by ten.
Answer 8 and explanation
No commas. Who borrowed tools identifies the members who must act. Commas would present borrowing tools as additional information about the members, which does not match the intended distinction.
The workshop has only one storage key, already known to the reader. Add punctuation to present its green tag as extra information: Our only storage key which has a green tag is in the drawer.
Answer 9 and explanation
Our only storage key, which has a green tag, is in the drawer. The key is already identified. Put commas before which and after tag; the second comma closes the inserted relative clause.
Correct the comma splice without changing the words: The door was locked, however, we had a spare key.
Answer 10 and explanation
The door was locked; however, we had a spare key. A full stop is also correct: The door was locked. However, we had a spare key. Each side is an independent clause; however alone cannot join them with a comma.
Join ideas while preserving the meaning
Maya was tired, so finishing the job was difficult; nevertheless, she finished it. Combine Maya was tired. She finished the job. into one sentence beginning with Although.
Answer 11 and explanation
Although Maya was tired, she finished the job. Although expresses the contrast in the brief. Because would claim tiredness caused her to finish, which the brief does not say. The initial adverbial clause takes a comma.
Several boys were waiting in different places. Only the boy standing by the gate waved. Combine The boy was standing by the gate. He waved. using a defining relative clause beginning with who.
Answer 12 and explanation
The boy who was standing by the gate waved. No commas: the relative clause identifies which boy. Who is the relative clause's subject and cannot simply be omitted. The boy that was standing by the gate waved is another grammatical version, but this prompt specifically asks for who.
A Short Classroom Writing Task
Write a three-sentence message about this fictional situation: a museum cancelled your group's visit because the building needed repairs; Nora, the organiser already known to your classmates, booked a library tour instead; the new tour starts at ten. Include one reason clause, one non-defining relative clause and one clause giving the content of what you know. Keep the facts unchanged.
One model and a checking guide
The museum cancelled our visit because the building needed repairs. Nora, who organised our trip, booked a library tour instead. We know that the new tour starts at ten.
The reason follows the main clause without a comma. Who organised our trip adds information about the already identified Nora and takes a pair of commas. That the new tour starts at ten gives the content of know. Other wording is acceptable if it keeps the facts and these functions.
For feedback, mark the function before the label: does the learner give a reason, identify or add information, and report content? Then check sentence boundaries and commas. If a learner misses questions 6–7, compare an introductory adverbial with a subject construction; for questions 8–9, revisit who or what is already identified in the context.
What to Practise Next
Use the subject-verb agreement chart and exercises if finding the subject is the problem, or sentence structure examples for fragments and sentence boundaries. The online grammar practice guide explains how teachers can assign existing grammar work in The Kingdom of English. These public exercises can be used directly on screen or printed; they are not an automatic import into a class.
Editorial note: this guide used AI-assisted drafting. The grammar explanations and original practice answers were checked against the linked sources on 21 October 2026. See our editorial approach.