The four types of sentences by structure
The structure depends on the clauses. An independent clause can stand alone as a sentence. A dependent clause starts with a word such as because, when, although, who or that, and can't stand alone.
| Type | Clauses | Example |
|---|---|---|
| Simple | One independent clause | My brother works in Dubai. |
| Compound | Two or more independent clauses | My brother works in Dubai, and my sister studies in Leeds. |
| Complex | One independent clause and at least one dependent clause | My brother moved to Dubai because he found a job there. |
| Compound-complex | Two or more independent clauses and at least one dependent clause | My brother moved to Dubai after he graduated, and my sister followed a year later. |
The four types of sentences by purpose
Every sentence also does a job, and its end punctuation usually shows which one.
| Type | Purpose | Ends with | Example |
|---|---|---|---|
| Declarative | Makes a statement | Full stop | The exam starts at ten. |
| Interrogative | Asks a question | Question mark | When does the exam start? |
| Imperative | Gives a command, instruction or request | Full stop, or an exclamation mark for force | Bring two pencils. |
| Exclamatory | Shows strong feeling | Exclamation mark | What a difficult paper that was! |
How the two systems fit together
Every sentence has both a structure and a purpose. "Close the window because it is cold" is a complex imperative sentence. "Did you pass, or do you need to retake it?" is a compound interrogative sentence.
A polite request often has a question form but works as a request: "Could you send me the file?" It still ends with a question mark.
Long does not mean complex. A simple sentence can be long if it has only one clause: "After a long day at the office, my exhausted father fell asleep on the sofa in front of the television."
Common mistakes
Wrong: The rent is high, many students share flats.
Right: The rent is high, so many students share flats.
Two independent clauses need a joining word such as so, or a full stop. A comma alone makes a comma splice.
Wrong: Because public transport is cheap.
Right: Many people commute by train because public transport is cheap.
A dependent clause on its own is a fragment, not a complex sentence.
Wrong: Although the city is crowded, but it is safe.
Right: Although the city is crowded, it is safe.
Although already links the clauses. Adding but doubles the link.
Wrong: Can you tell me where is the station?
Right: Can you tell me where the station is?
Inside a longer question, the hidden question uses statement word order.
Using this in IELTS and PTE
The public IELTS Writing band descriptors for Grammatical Range and Accuracy refer to the range of structures you use and how accurately you use them, including a mix of simple and complex sentence forms. That doesn't mean every sentence should be long. Examiners look for control, so a clear simple sentence beats a tangled compound-complex one. In IELTS Speaking, natural complex sentences ("I moved to Pune because the jobs were better") show range without sounding rehearsed. In PTE Summarize Written Text, your single sentence will usually need to be complex or compound to cover the main points.
5 questions
Exercise
Try each one, then open it to check your answer.
1. Name the structure: "The shop was closed, so we went home."
Compound.
Two independent clauses are joined by so.
2. Name the structure: "I'll call you when I land."
Complex.
One independent clause plus the dependent clause when I land.
3. Name the purpose: "Turn off your phone before the test."
Imperative.
It gives an instruction, and the subject you is understood.
4. Name the structure: "Students in the morning group and the evening group take the same test."
Simple.
It has only one clause, with one subject and one verb, however long it is.
5. Name the purpose: "How quickly the year has gone!"
Exclamatory.
It expresses strong feeling and ends with an exclamation mark.
Frequently asked questions
What is the difference between a compound and a complex sentence?+
A compound sentence joins two independent clauses, usually with and, but, or or so. A complex sentence joins an independent clause to a dependent one, using a word such as because, if, when or although.
How many types of sentences are there?+
There are four by structure (simple, compound, complex, compound-complex) and four by purpose (declarative, interrogative, imperative, exclamatory). Every sentence belongs to one group in each system.
Should I use only complex sentences in IELTS Writing?+
No. The band descriptors mention a mix of sentence forms. Accurate complex sentences show range, but simple sentences are useful for clear, direct points.
Is an exclamatory sentence the same as an imperative one?+
No. An imperative gives a command ("Stop talking."). An exclamatory sentence expresses feeling ("What a noise!"). An imperative can end with an exclamation mark, but it is still a command.
Keep going
More grammar lessons
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