An adverbial clause is a subordinate clause that modifies the main verb of a sentence, answering questions like when?, why?, how? or under what conditions? As Cambridge Grammar notes, adverbial clauses are introduced by a subordinating conjunction and always contain their own subject and verb. Mastering the five main types unlocks a huge range of complex, accurate sentences for writing and speaking. For example, in the sentence "Although it was raining, we went for a walk," the clause Although it was raining has its own subject and verb and modifies the main clause, showing concession. This must not be confused with an adverbial phrase, which has no subject and verb of its own, e.g. "in spite of the rain."
What Is an Adverbial Clause?
An adverbial clause is a dependent clause that functions like an adverb — it modifies the main verb and gives extra information about the circumstances of the action. It always contains a subject and a finite verb, and it is introduced by a subordinating conjunction (when, because, if, although, so that). It cannot stand alone as a sentence.
Time Clauses
Time clauses tell us when something happens. Common conjunctions: when, while, after, before, until, as soon as, once, as, by the time. An important rule: in time clauses referring to the future, use present simple (not will). When she arrives, we will start. After you have eaten, wash up. I will wait until you are ready.
- when — a single point or completed action: When the phone rang, she picked it up.
- while — a background action in progress: While I was cooking, he arrived.
- as soon as / once — immediately after: As soon as she lands, call me.
- until / till — up to a point: Stay here until I get back.
Reason Clauses
Reason clauses answer why and are introduced by because, since, as. Use because for the main, essential reason (often new information). Use since or as when the reason is already known or obvious. Because it was cold, he wore a coat. Since you are here, let us begin. As she is a doctor, she understood immediately.
Condition Clauses
Condition clauses set the conditions under which something happens. Key conjunctions: if, unless, as long as, provided that, on condition that. Unless means if not and introduces a negative condition. Unless you hurry, you will be late. As long as you study, you will improve. Provided that all documents are submitted, the application will proceed.
Concession Clauses
Concession clauses introduce a contrast or unexpected result. Conjunctions: although, even though, though, while, whereas. Note that you cannot use both although and but in the same sentence. Although she studied hard, she failed. Even though it rained, we went out. Whereas the north is cold, the south is warm.
Purpose Clauses
Purpose clauses explain why someone does something (the aim or goal). Conjunctions: so that, in order that, in case. These are followed by a subject and a modal verb (can, could, will, would, might). He spoke slowly so that everyone could understand. Take an umbrella in case it rains. She saved money in order that she could study abroad.
Common Mistakes
- Wrong: When she will arrive, we will start. Correct: When she arrives, we will start. (present simple in time clause, not will)
- Wrong: Although it was cold, but she did not wear a coat. Correct: Although it was cold, she did not wear a coat. (no but after although)
- Wrong: He left early for to catch the train. Correct: He left early so that he could catch the train.
Practice Exercises
Grammar Quiz
Choose the correct conjunction to complete adverbial clause sentences.
Cloze Dropdown
Fill in the missing conjunctions in context passages.
Unjumble
Reorder words to form correct adverbial clause sentences.
Complete the Sentence
Add the correct clause type to complete each sentence.
Practice What You've Learned
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Frequently Asked Questions
What is an adverbial clause?
A subordinate clause that modifies the main verb like an adverb, telling us when, why, how, or under what conditions something happens. It always contains a subject and verb and is introduced by a subordinating conjunction.
What is the difference between 'when' and 'while' in time clauses?
'When' introduces a single completed action or a point in time: When the phone rang, she picked it up. 'While' introduces a background action in progress: While I was cooking, he arrived. Use while with continuous tenses to show that one action is the backdrop for another.
Can I start a sentence with 'because'?
Yes, absolutely. Starting a sentence with 'because' is grammatically correct when it introduces an adverbial clause followed by a complete main clause: Because it rained heavily, the match was cancelled. The old rule against it was a style preference for formal writing, not a grammar law. However, avoid using 'because' alone as a sentence fragment.
What is the difference between 'although' and 'even though'?
Both introduce concession clauses showing contrast, but 'even though' is stronger and more emphatic. Although she was tired, she finished. Even though she had a fever, she came to work (stronger surprise/contrast). 'Though' is more informal and can also be used at the end of a sentence: She was tired, though.
What is a purpose clause and how do I form it?
A purpose clause explains why someone does something. Form: main clause + so that/in order that + subject + modal (can/could/will/would): He saved money so that he could buy a car. 'In case' expresses precaution: Take your phone in case you get lost.
When do I use 'since' vs 'because' in reason clauses?
Both introduce reasons, but 'since' and 'as' are used when the reason is already known or obvious to the reader: Since you are a doctor, you understand the risks. 'Because' introduces new or essential information about the cause: She left because she was ill. In formal writing, avoid 'since' for reason if there could be ambiguity with 'since' meaning 'from a time in the past'.
Do adverbial clauses need a comma?
When the adverbial clause comes before the main clause, use a comma: Although it rained, we went out. When the adverbial clause follows the main clause, a comma is usually not needed: We went out although it rained. Time clauses, reason clauses, and concession clauses at the start of a sentence always take a comma.
What is the difference between 'unless' and 'if not'?
'Unless' means 'except if' and introduces a negative condition: Unless you hurry (= if you do not hurry), you will be late. It cannot always replace 'if not' — use 'unless' only when the condition is the sole exception to a positive statement. Avoid double negatives: do not say 'unless you don't hurry'.
What are reduced adverbial clauses?
A reduced adverbial clause drops the subject and changes the verb to a participle: While she was walking = While walking. After he had eaten = After eating. This is possible only when the subject of both clauses is the same. Reduced clauses are common in formal writing.
How do adverbial clauses help in IELTS and Cambridge exams?
Using a variety of adverbial clause types demonstrates complex sentence structures and grammatical range. Examiners at B2-C1 level expect candidates to use concession (although/even though), purpose (so that/in order to), and time/condition subordination accurately and fluently.