There are four kinds of conditional sentences in English.
1: The Zero Conditional:
We make it with: if + present simple, … present simple
For example: If you sit in the sun for too long, you get burned.
We use the zero conditional when we’re talking about a result that will always happen. If the first part of the sentence is true then the second will always follow. If you sit in the sun for too long, you’ll always get burned – it’s a natural consequence.
Here are some more examples:
If you heat water to 100%, it boils.
If we eat too much, we put on weight.
If I eat peanuts, I get sick.
If you mix hydrogen and oxygen, you get water.
Things to note:
With the zero conditional we are talking in general, not about one particular instance.
We can usually replace the ‘if’ with ‘when’ without changing the meaning.
We can change the order of the two parts: it’s fine to say: You get water if you mix hydrogen and oxygen.
2: The First Conditional:
We make it with: if + present simple, … will + infinitive
For example: If it rains tomorrow, we’ll go to the cinema.
We use the first conditional to talk about things that might happen in the future. Of course, we can’t know exactly what will happen in the future, but this describes possible things that might come true.
Here are some more examples:
If I have enough money, I’ll buy a new dress.
If the train is delayed, we’ll be late.
If she doesn’t study, she’ll fail the exam.
If John keeps eating chocolate, he’ll be sick.
Things to note:
We can also change the order of the two parts in the first conditional:
I’ll buy a new dress if I have enough money.
3: The Second Conditional:
We make it with: if + past simple, … would + infinitive
For example: If I had a lot of money, I would travel around the world.
We use the second conditional in two situations:
1) to talk about things in the future that probably won’t happen. It could be that I’m imagining something I’d like that’s very unlikely.
For example: If I won the lottery, I would buy a big house.
Another example: If I met George Clooney, I would marry him.
2) to talk about something in the present that is impossible, because the first part of the sentence isn’t true.
For example: If I had her number, I would call her (but I don’t have her number)
Another example: If I had enough time, I would help you.
Things to note:
With the verb ‘be’, when we use ‘I’ and ‘he / she / it’ after the ‘if’ and before the past simple, we often use ‘were’ and not ‘was’.
For example: If I were you, I wouldn’t take that job.
We can also swap the order in the second conditional: I would travel around the world if I had a lot of money.
4: The Third Conditional:
We make it with: if + past perfect, … would + have + past participle
For example: If I had gone to bed early, I would have caught the train.
We use the third conditional to talk about the past, and to describe a situation that didn’t happen, and to imagine the result of this situation.
Here are some more examples:
If she had studied, she would have passed the exam (but, really we know she didn’t study and so she didn’t pass)
If I hadn’t studied English, I wouldn’t have become a teacher (but I did study English).
If we’d woken up earlier, we wouldn’t have missed the plane.
If they’d gone to bed at ten, they wouldn’t be so tired today.
Things to note:
We can change the order with the third conditional too: I would have caught the train if I’d gone to bed early.