sentences state a condition and its result, usually with if. English has four main types, numbered zero to three, plus mixed conditionals. The type you choose depends on whether the situation is always true, a real future possibility, an unreal present, or an unreal past.
The big picture
Every sentence has two clauses: the if clause, which gives the condition, and the main clause, which gives the result. The tense in each clause tells the listener how real the situation is.
The zero conditional is for things that are always true. The first conditional is for real possibilities in the future. The second conditional is for unreal or unlikely situations in the present or future. The third conditional is for unreal situations in the past. Mixed conditionals combine the second and the third.
Use this page as a map, and then follow the links to the full guide for each type.
Zero conditional: always true
Form: if + present simple, present simple. Use it for facts, rules and habits: If you heat ice, it melts. If the page does not load, refresh the browser. In this pattern, when can replace if.
Typical mistake: putting will in the if clause.
First conditional: real future possibility
Form: if + present simple, will + base verb. Use it for a real possibility in the future: If it rains tomorrow, we will stay at home. If the government raises taxes, spending will fall.
Typical mistake: using will after if, as in If it will rain. The if clause stays in the present simple, even when the meaning is about the future. Unless means if not, so Unless you hurry, you will miss the train is correct.
Second conditional: unreal present or future
Form: if + past simple, would + base verb. Use it for unlikely or imaginary situations and for advice: If I lived by the sea, I would swim every day. If I were you, I would take the job.
Typical mistake: using would in the if clause. Remember that the past form signals an unreal situation, not past time.
Third conditional: unreal past
Form: if + past perfect, would have + . Use it for regrets and for how the past could have been different: If she had left earlier, she would have caught the train.
Typical mistake: using would have in the if clause, as in If I would have known.
Mixed conditionals
Mixed join a past condition to a present result, or the other way round. The most common type is a past condition with a present result: If I had taken that job, I would be living in Dublin now. The if clause is the third conditional form, and the main clause is the second conditional form.
The other type is a present condition with a past result: If she were more careful, she would not have lost the keys. You do not need mixed conditionals often, so learn the four main types first.
Other ways to introduce a condition
If is not the only word. Unless means if not. As long as and provided that mean only if: You can borrow the book as long as you return it on Friday. In case means as a precaution: Take an umbrella in case it rains. Suppose or supposing can open a question: Suppose you lost your phone, what would you do?
You can also use other in the main clause. If you finish early, you can leave. If the weather is bad, we might cancel. If you want to improve your listening, you should watch a short video every day. These give you more ways to express advice, permission and possibility.
How to choose the right type
Ask two questions. Is the situation real or imaginary? And is it about the past, the present or the future?
If it is always true, use the zero . If it is a real possibility in the future, use the first. If it is imaginary now or in the future, use the second. If it is imaginary in the past, use the third. This works in speech and in writing, and it also helps you notice an error when you read your own answer.
Who finds this hard?
- Chinese speakers: Chinese does not change the verb to mark real and unreal conditions, so each English pattern is a new tense habit.
IELTS tip
In Speaking Part 3, a answer lets you explore a situation in one sentence, such as If cities had more green space, people would be healthier. In Writing Task 2, use one or two conditionals in your solution or discussion paragraphs, and check the verb forms in both clauses.
Frequently asked questions
How many conditionals are there in English?
Teachers usually describe four main types, numbered zero to three, and then mixed . Learn the four main types first.
Which conditional is most useful for IELTS?
The first and second conditionals are very useful for speaking and writing, since they let you discuss real and imaginary situations.
Can I use when instead of if?
In the zero conditional, yes. In the first conditional, when means you are sure it will happen, and if means it is only possible.
Do I always need a comma?
Use a comma after the if clause when it comes first. Do not use a comma when the main clause comes first.
Sources
- Swan, M. (2016). Practical English Usage (4th ed.). Oxford University Press.
- Murphy, R. (2019). English Grammar in Use (5th ed.). Cambridge University Press.