1. Lesson Overview
In this lesson, you will learn how complex sentences are formed through subordination.
A complex sentence contains:
-
one independent clause
-
one or more dependent clauses
Dependent clauses are introduced by subordinating conjunctions, which show logical relationships such as cause, contrast, condition, time, purpose, or result.
Example:
The experiment succeeded because the method was accurate.
| Clause | Type |
|---|---|
| The experiment succeeded | Independent clause |
| because the method was accurate | Dependent clause |
Complex sentences allow writers to connect ideas logically and express relationships clearly.
By the end of this lesson, you will be able to:
-
recognise how dependent clauses form complex sentences
-
use subordinating conjunctions correctly
-
express logical relationships such as cause, contrast, condition, and time
-
avoid common errors involving subordination
2. Concept Introduction
Consider these two sentences:
The experiment succeeded. The method was accurate.
These sentences can be combined into a complex sentence:
The experiment succeeded because the method was accurate.
| Clause | Type |
|---|---|
| The experiment succeeded | Independent clause |
| because the method was accurate | Dependent clause |
The conjunction because shows a cause–effect relationship.
3. Core Explanation
A complex sentence links an independent clause with a dependent clause using a subordinating conjunction.
Basic structure:
Independent Clause + Subordinating Conjunction + Dependent Clause
Example:
The experiment was repeated because the results were inconsistent.
The dependent clause provides additional information about the main clause.
Complex sentences help writers express relationships such as:
-
cause
-
contrast
-
condition
-
time
-
purpose
4. Rule Table
Structure of Complex Sentences
| Structure | Example |
|---|---|
| Independent clause + dependent clause | The experiment failed because the equipment malfunctioned. |
| Dependent clause + independent clause | Because the equipment malfunctioned, the experiment failed. |
Common Subordinating Conjunctions
| Conjunction | Relationship | Example |
|---|---|---|
| because | cause | The experiment failed because the data were incorrect. |
| although | contrast | Although the method was complex, the results were accurate. |
| if | condition | If the test succeeds, the theory will be confirmed. |
| when | time | The results were recorded when the experiment ended. |
| while | simultaneous action | The technician monitored the system while the test was running. |
| since | reason/time | Since the equipment failed, the experiment stopped. |
| unless | condition | The results will remain uncertain unless further tests are conducted. |
5. Usage
1. Expressing cause
Example:
The experiment failed because the equipment malfunctioned.
2. Expressing contrast
Example:
Although the procedure was complex, the results were reliable.
3. Expressing conditions
Example:
If the results are consistent, the theory will be accepted.
4. Expressing time
Example:
The data were analysed after the experiment ended.
5. Expressing simultaneous actions
Example:
The technician monitored the system while the experiment was running.
6. Signal Words
Subordinating conjunctions signal relationships between clauses.
| Conjunction | Function | Example |
|---|---|---|
| because | cause | because the equipment failed |
| although | contrast | although the method was new |
| if | condition | if the experiment succeeds |
| when | time | when the test ended |
| while | simultaneous action | while the system was running |
| since | cause/time | since the method changed |
| unless | negative condition | unless further research is conducted |
7. Special Cases
Dependent Clause at the Beginning
When a dependent clause appears first, it is usually followed by a comma.
Example:
Although the experiment was difficult, the results were valuable.
Reversed order:
The results were valuable although the experiment was difficult.
Multiple Dependent Clauses
Complex sentences may contain more than one dependent clause.
Example:
The experiment succeeded because the researchers followed the procedure carefully when the equipment was calibrated correctly.
This sentence contains:
-
one independent clause
-
two dependent clauses
8. Additional Notes
Complex sentences help writers express logical relationships between ideas, which improves clarity and academic writing.
Example:
Separate sentences:
The experiment failed. The equipment malfunctioned.
Complex sentence:
The experiment failed because the equipment malfunctioned.
Using subordination helps avoid repetitive sentence structures and improves writing style.
9. Common Errors
⚠ Sentence fragment
Incorrect:
Because the experiment failed.
Correct:
The experiment was repeated because it failed.
Explanation:
Dependent clauses cannot stand alone.
⚠ Missing comma after introductory clause
Incorrect:
Although the method was accurate the experiment failed.
Correct:
Although the method was accurate, the experiment failed.
Explanation:
A comma separates the clauses when the dependent clause appears first.
⚠ Incorrect conjunction choice
Incorrect:
The experiment failed although the equipment malfunctioned.
Correct:
The experiment failed because the equipment malfunctioned.
Explanation:
Choose conjunctions that express the correct relationship.
⚠ Incorrect clause order
Incorrect:
Because failed the experiment.
Correct:
Because the experiment failed.
Explanation:
Clauses must follow subject–verb order.
⚠ Incomplete complex sentence
Incorrect:
Although the results were promising.
Correct:
Although the results were promising, additional tests were required.
Explanation:
Dependent clauses must connect to independent clauses.
10. Lesson Mastery
After completing this lesson, you should now be able to:
✅ recognise how dependent clauses form complex sentences
✅ use subordinating conjunctions correctly
✅ express relationships such as cause, contrast, condition, and time
✅ avoid common errors involving subordination