A clause is a group of words that contains a subject and a verb. Clauses are the building blocks of sentences. Once you understand them, you can write longer, clearer sentences and fix common errors like fragments and run-ons.
This guide explains the main types of clauses in simple English, shows how they build different kinds of sentences, and gives you practice with answers.
Clause vs Phrase
- She laughed. → a clause (subject: she; verb: laughed)
- after the lesson → a phrase (no subject-verb pair)
A phrase is a group of words without a subject and verb working together. A clause always has both.
Independent (Main) Clauses
An independent clause expresses a complete thought and can stand alone as a sentence.
- I finished my homework.
- The train was late.
Dependent (Subordinate) Clauses
A dependent clause has a subject and a verb, but it cannot stand alone. It depends on a main clause. It usually starts with a word like because, although, when, if, who, which or that.
- because I was tired
- when the rain stopped
Three Types of Dependent Clause
| Type | Job | Example |
|---|---|---|
| Adverb clause | Says when, why, how, or under what condition | I stayed home because it was raining. |
| Adjective (relative) clause | Describes a noun | The book that you lent me was great. |
| Noun clause | Acts as a noun (subject or object) | I know what you mean. |
Common Words That Start Adverb Clauses
- Time: when, while, before, after, until, as soon as
- Reason: because, since, as
- Condition: if, unless
- Contrast: although, though, even though, whereas
- Purpose: so that
For more on adjective clauses, read our guide to relative clauses.
How Clauses Build Sentences
- Simple sentence: one independent clause. The bus was late.
- Compound sentence: two independent clauses joined by and, but, or, so or a semicolon. The bus was late, so I walked.
- Complex sentence: one independent clause plus at least one dependent clause. Because the bus was late, I walked.
- Compound-complex sentence: two or more independent clauses and at least one dependent clause. Because the bus was late, I walked, and I still arrived on time.
Using a mix of these types makes your writing more interesting. Learn more in how to structure sentences in English.
Punctuation Tips
- When a dependent clause comes first, put a comma after it: If it rains, we will stay inside.
- When it comes second, you usually do not need a comma: We will stay inside if it rains.
- Join two independent clauses with a comma + joining word, or a semicolon: It rained, so we stayed in. / It rained; we stayed in.
Common Mistakes
Sentence Fragments
A dependent clause alone is not a sentence.
- Because I forgot my keys. → I was locked out because I forgot my keys.
Run-On Sentences and Comma Splices
- I was hungry I ate lunch. → I was hungry, so I ate lunch.
- It was late, we went home. → It was late, so we went home.
See more in our list of common grammar mistakes.
Practice
Is the underlined part an independent clause (I), dependent clause (D) or phrase (P)?
- After dinner, we watched TV.
- When she arrived, the class had started.
- I like tea, but my brother likes coffee.
- The man who called was my uncle.
Answers: 1. P 2. D 3. I 4. D (adjective clause)
Free Resources
The British Council’s LearnEnglish grammar lessons include clause practice by level. Purdue OWL’s grammar guide explains clauses and sentence types, and its grammar exercises help you check your understanding.
Final Thoughts
Every clause has a subject and a verb. Independent clauses can stand alone; dependent clauses need a main clause. Combine them to make compound and complex sentences, and use commas correctly to avoid fragments and run-ons.
