A conditional sentence contains two clauses, one is the principal clause and the other is the sub-ordinate clause. The sub-ordinate clause mainly begins with IF and it expresses condition. The main clause indicates the result of the condition.
Read the following three sentences:
- If you read, you will pass.
- If you waste your time, you will suffer in future.
- If you fail, your mother will be unhappy.
The If-clause is at the beginning of the above sentences and there is a comma (,) between the clauses. If we wish, we can also write the if-clauses after the main clause. Then no comma (,) is needed between the clauses.
- You will pass if you read.
- You will suffer in future If you waste your time.
- Your mother will be unhappy if you fail.
Types of Conditional Sentences
There are four types of Conditional Sentences in English:
1. Zero Conditional
If + present + present
- If you boil water, it becomes steam.
- If the sun rises, darkness goes away.
We use zero conditional when we talk about things that are true. Both the clauses of a zero conditional are in the present simple tense. A zero conditional expresses present time.
2. First Conditional
If + Present + Future
- If you want, I will help you.
- If you read, you will learn.
We use first conditional when we talk about things that are true or possible. The if-clause is in the present simple tense. The main clause is in the future tense. A first conditional expresses future time.
3. Second Conditional
If + Past + would/ could/ might
- If I won the lottery, I would buy a car.
- If she knew the answer, she would tell us.
- If I were a bird, I would fly to you.
We use second conditional when we talk about things that are untrue or impossible. The if-clause is in the past simple tense. The main clause has would/ could/ might before the main verb. A second conditional expresses present or future time, so, we say that the second conditional sentences have unreal past tense.
4. Third Conditional
If + Past Perfect + would have/ could have/ might have
- If Lucy had got enough money, she would have bought a new car.
- If I had won the lottery, I would have bought a house.
We use third conditional when we talk about things that were untrue or impossible in the past. The if-clause is in the past perfect tense. The main clause has would have/ could have/ might have before the past participle of the main verb. A third conditional expresses past time.