A conditional sentence has two parts: the if-clause, which describes a condition, and the main clause, which describes the result. English has four main patterns, usually called the zero, first, second and third conditionals. The tenses you choose show how real or likely the situation is.
A simple way to choose is to ask: "Is this always true, possible in the future, imaginary, or already in the past and impossible to change?" Remember one key rule too: the if-clause does not normally take will or would, even when the meaning is future or imaginary.
How to form conditionals
Each type has its own pattern of tenses. The base verb is the verb without to (go, be, have). The if-clause can come first or second; the meaning stays the same.
| Type | Pattern | Example |
|---|---|---|
| Zero conditional | If + present simple, present simple | If you heat ice, it melts. |
| First conditional | If + present simple, will + base verb | If it rains tomorrow, we'll stay inside. |
| Second conditional | If + past simple, would + base verb | If I had more free time, I would learn to paint. |
| Third conditional | If + past perfect, would have + past participle | If we had left earlier, we would have caught the train. |
| Mixed conditional | If + past perfect, would + base verb (past condition, present result) | If I had taken that job, I would live in Paris now. |
- Comma rule: when the if-clause comes first, put a comma after it (If it rains, we'll stay inside). When the main clause comes first, you usually don't need a comma (We'll stay inside if it rains).
- No will or would in the if-clause: say If I see her (not If I will see her) and If I had known (not If I would have known).
- If I were you: in the second conditional, were is often used for all persons (if I were, if she were), especially in formal English. If I were you, I'd... is the standard way to give advice.
- Contractions: I'll, you'll, won't; I'd, she'd, wouldn't. In the third conditional, I'd can mean I had or I would: If I'd known (= I had known), I'd have helped (= I would have helped).
- Use might or could instead of will or would when the result is less certain or is about ability: If you leave now, you might catch the bus. If I had a car, I could drive you.
When to use conditionals
1. Zero conditional: facts and general truths
Use the zero conditional for things that are always true, such as scientific facts and habits. Here if means the same as when or every time.
- If you mix blue and yellow, you get green.
- If I drink coffee in the evening, I can't sleep.
- Plants die if they don't get enough light.
2. First conditional: real possibilities in the future
Use the first conditional when the condition is possible and the result is likely. It is common for plans, warnings, promises and offers.
- If the weather is nice on Saturday, we'll have a picnic.
- If you don't hurry, you'll miss the bus.
- I'll call you if I hear any news.
3. Second conditional: imaginary or unlikely situations
Use the second conditional for situations that are not true now or are unlikely to happen. The past simple here does not mean past time; it shows that the situation is imaginary. If I were you is the usual way to give advice.
- If I lived near the sea, I would swim every morning.
- What would you do if you won the lottery?
- If I were you, I'd take the job.
4. Third conditional: imagining a different past
Use the third conditional to talk about a past that did not happen. Because the past cannot change, both the condition and the result are impossible. It is often used for regrets and criticism.
- If I had studied harder, I would have passed the exam.
- She wouldn't have been late if she had taken a taxi.
- If you had told me about the party, I would have come.
5. Mixed conditionals: a past condition with a present result
Sometimes an imaginary past would change the present. Then you combine the two patterns: if + past perfect, would + base verb. The opposite mix is also possible: a present situation with an imaginary past result.
- If I had gone to bed earlier, I wouldn't be so tired now.
- If we had bought that house, we would be neighbors now.
- If I weren't afraid of flying, I would have gone with them. (present situation, past result)
6. Unless, as long as and provided that
Unless means if ... not. As long as and provided (that) mean only if; they make the condition stronger. All of them follow the same tense rules as if.
- You won't get a seat unless you book early. (= if you don't book early)
- You can borrow my car as long as you bring it back by six.
- Provided that it doesn't rain, the concert will take place outside.
Words that introduce a condition
- if
- unless
- as long as
- provided (that)
- providing (that)
- on condition that
- only if
- even if
- suppose / supposing
- what if
- when
- in case
When is for things you are sure will happen (When I get home, I'll call you); if is for things that may happen. In case is different from if: it means "to be ready because something might happen" (Take an umbrella in case it rains).
Examples
Positive
- If you freeze water, it turns into ice.
- If I finish work early, I'll meet you for dinner.
- If we had a garden, we would grow our own vegetables.
- If they had asked for directions, they would have arrived on time.
Negative
- If it doesn't rain soon, the plants will die.
- I won't go to the party unless you come with me.
- If he didn't live so far away, we would see him more often.
- We wouldn't have missed the flight if the taxi hadn't broken down.
Questions
- What do you do if you can't sleep?
- Will you call me if the train is late?
- What would you do if you lost your phone?
- Would you have accepted the offer if they had paid you more?
First or second conditional?
Both talk about the present or the future. The difference is how real the situation feels to the speaker: the first conditional is for things that can really happen, and the second is for things that are imaginary, impossible or very unlikely. Sometimes both are possible, and the choice shows what the speaker thinks.
| First conditional | Second conditional |
|---|---|
| If I get the job, I'll move to Berlin. (I have an interview; it's possible) | If I got the job, I'd move to Berlin. (I don't think I'll get it) |
| If it's sunny tomorrow, we'll go to the beach. (a real plan) | If I lived by the beach, I'd go every day. (I don't live by the beach) |
| If you practice every day, you'll improve quickly. (advice about a real situation) | If I were a teacher, I'd give less homework. (I'm not a teacher) |
| What will you do if you miss the bus? (it could happen) | What would you do if you saw a ghost? (very unlikely) |
Common mistakes
- WrongIf I will see him, I will tell him.RightIf I see him, I will tell him.
In a first conditional, the if-clause uses the present simple, not will, even though it refers to the future.
- WrongIf I would have known, I would have helped you.RightIf I had known, I would have helped you.
The if-clause of the third conditional takes the past perfect (had known), not would have.
- WrongIf I would have more time, I would read more.RightIf I had more time, I would read more.
In the second conditional, the if-clause takes the past simple; would belongs only in the main clause.
- WrongIf I had more money, I will buy a new laptop.RightIf I had more money, I would buy a new laptop.
A past simple if-clause goes with would, not will, so don't mix the first and second conditionals.
- WrongIf she had left earlier, she would catch the train last night.RightIf she had left earlier, she would have caught the train last night.
When both parts are about the past, the main clause needs would have + past participle.
- WrongUnless you don't hurry, you will miss the train.RightUnless you hurry, you will miss the train.
Unless already means if not, so don't add another negative.
The missed flight
Examples of conditionals are highlighted.
Last summer, Leo missed his flight to Rome. If he had checked the time, he would have left home earlier. If he hadn't stopped for coffee, he would have caught the airport train. Now he tells the story as a joke. "If you travel with me, you'll never be bored," he says. His sister is less amused. "If I were you, I would set three alarms," she tells him. But Leo has a theory. If he hadn't missed that flight, he wouldn't have met Clara at the airport bookstore, and he wouldn't be married to her now. "If you lose something, you often find something better," he says. His sister smiles. "Fine. But if you miss our flight next month, I'll go without you."
Conditionals quiz
8 questions. Choose an answer to see if it is right and why.
Read texts that use conditionals
Grammar sticks when you meet it again in real reading. These graded texts use this structure; each one has key words, audio and questions.
Conditionals: questions and answers
What are the four types of conditionals?
The zero conditional (If + present simple, present simple) is for general truths, and the first (If + present simple, will) is for real future possibilities. The second (If + past simple, would) is for imaginary present or future situations, and the third (If + past perfect, would have + past participle) is for imaginary past situations.
Can I use will or would after if?
Usually not. In the if-clause, use the present simple instead of will (If it rains, not If it will rain) and a past form instead of would (If I had time, not If I would have time). Will and would normally belong in the main clause.
Is it "If I was" or "If I were"?
Both are used in the second conditional. If I were is the traditional form, preferred in formal writing and in the fixed phrase If I were you; If I was is common in informal speech.
What does unless mean?
Unless means if ... not: "You won't pass unless you study" means "You won't pass if you don't study." Because unless already includes the idea of not, don't say unless you don't study.
Do I need a comma in a conditional sentence?
Put a comma after the if-clause when it comes first: If you need help, call me. When the main clause comes first, you usually don't need a comma: Call me if you need help.