We use conditional sentences to express that a certain situation (the main clause) can only take place if a certain condition (if clause) is met before. We have four different kinds of conditional sentences called Zero, First, Second or Third Conditional -or Type 0, I, II, III. the difference in meaning between these clauses is whether the speaker believes the condition to be more or less possible.
Below, you can find the four different kinds of conditional clauses with an explanation of its form and function.
We use the zero conditional to talk about general facts, not specific situations, for instance, natural laws. Sometimes, we use “when” or “whenever” instead of “if”.
- If/When/Whenever you heat water, it boils.
- If/When/Whenever it rains, the ground gets wet.
- If/When/Whenever you don’t sleep well, you are tired.
We us the First Conditional to talk about specific situations. Both the condition and the result are seen as real and possible by the speaker.
- If you go to the party, you will meet very interesting people there.
- If you study hard, you will pass all your exams.
- If you tell her a secret, she will tell everybody.
Sometimes, instead of “if”, we use the connector “unless”. Compare the following sentences:
- If he does not get here soon, he will miss the train.
- Unless he gets here soon, he will miss the train.
We use the second conditional to talk about an unreal situation and its probable result. Both the condition and result are seen as unlikely by the speaker.
- If I had a lot of money, I would buy a new car.
- If she changed her attitude, she would have more friends.
- If they helped us, we would finish in about an hour.
If the verb in the “if” clause is the verb to be, we can use “were” with all subjects. It is a more formal option.
- If I were you, I would tell her the truth.
- If Jack were here, he would know what to do.
We use the third condional to make hypothesis about the past. Both the condition and the consequence are impossible because they happened in the past
- If I had known how, I would have helped you.
- If they had not been late, they would have seen the whole film.
- If John had told me, I wouldn’t have done it.
Whatever the kind of conditional, we can change the order in which we use the sentences. In other words, we can start with the “if” clause, or not. However, it is really important to keep the verb tenses correct. Compare these sentences:
- If you press the button, the machine starts.
- The machine starts if you press the button.
- I will call you if she comes.
- If she comes, I will call.
- I wouldn’t tell you if I knew!
- If I knew, I wouldn’t tell you!
- I would have arrived on time if I hadn’t missed the train.
- If I hadn’t missed the train, I would have arrived on time.
When we start with the “if” clause, we usually use a comma between clauses. This is not necessary when the “if” clause is at the end.
You can download this information if pdf format by clicking on “conditionals“.