Conditional Sentences in English : Definition, Types, Structure & Examples

What is a conditional?

A conditional is a sentence or part of a sentence that expresses a condition. It usually begins with the words “when,” “if” and “unless.” A condition is what must happen before something else can happen. For examples:

1. I will come if I have enough time.
   (I am not sure that I will come. It depends on something else.)
2. She would tell me if she knew.
   (She does not know.)
3. Unless she agrees to pay us, we will not take the job.
   (She must agree to pay before we take the job.)
4. They will come when I call them.
   (They will not come before I call them.)
    

4 Basic conditionals

There are four basic conditionals in English, or in other words: there are four ways to express that something is dependent on something else.

1. The Zero Conditional

“If the sun sets, it becomes night.” We use the zero conditional when talking about things that are always true, or generally true.
Structure: If + Simple Present, + Simple Present     OR     Simple Present + If + Simple Present
Examples:

1. If you boil an egg, it becomes solid.
2. If you heat something, it becomes hotter.
3. I always listen to music if I jog.

Note: We can use “when” instead of “if.” Examples:

1. When I see Karen, I always feel better.
2. When she feels sick, she lies in bed.
3. He starts yelling only when he gets really desperate.

2. The First Conditional

“If I see Sam, I will ask him to give you a call.” We use the first conditional when talking about possible future events.
Structure: If + Simple Present, + Will     OR     Will + If + Simple Present
Examples:

1. Lisa will be very happy if she wins the prize.
2. If it rains, then we will stay at home.
3. You will always be able to take another test if you fail.
4. If I see Sam, I will ask him to give you a call.

Note: You can use these modal verbs instead of will: shall, can, may. Examples:

1. If you fail, you can always try again.
2. If you finish everything on time, you may go home earlier.
3. We shall meet on Sunday if it is alright with you

3. The Second Conditional

“If I met a genie, I would ask for infinite wealth…” We use the second conditional when talking about future events that are not likely to happen.
Structure: If + Simple Past, + Would + Base Form     OR     Would + Base Form + If + Simple Past
Examples:

1. If I won a million dollars, I would travel around the world.
   (There is a small possibility that I would actually win.)
2. If I met him again, I would tell him the truth.
   (There is a small possibility that I would actually meet him again.)
3. She would quit school if her parents agreed.
   (It is unlikely that her parents will agree.)
4. I would be surprised if I saw pigs in the sky.
   (It is very unlikely for me to see pigs in the sky.)

We also use the second conditional when talking about things which are contrary to the present facts. “If I had any money, I would give you some.” Examples:

1. If she worked less, she wouldn’t be so tired.
   (In reality, she doesn’t work less, so she is tired.)
2. You would see John if you were here now.
   (In reality, you are not here now, so you don’t see John.)
3. If things were different, we would be happy.
   (In reality, things are not different, and we are not happy.)
4. We would be good friends if she were nicer.
   (In reality, she is not nice, and we are not good friends.)

Note: You can use these modal verbs instead of would: should, could, might. Examples:

• If she did not have her job, she could come with us to the North Pole.
• If they wanted to move, they could sell the house to us.

The verb BE
The verb “be” has a special rule in this case. Usually we say: I was, he was, she was, it was, we were, you were, they were. However, in some cases, we use: I were, he were, she were, it were, we were, you were, they were. In other words: “were” is the form when talking about imaginary circumstances. Examples

1. If I were you, I would apologize. (In reality, I am not you.)
2. I would fight back, if I were you. (In reality, I am not you.)

4. The Third Conditional

“If I had paid more attention, I would not have hit myself…” We use the third conditional when talking about things which are contrary to the past facts. In other words: events that did not happen in the past.
Structure: If + Past Perfect, + Would have + V3     OR     Would have + V3 + If + Past Perfect
Examples:

1. If I had woken up on time, I would have taken the bus.
   (What really happened was that I did not wake up on time, and so I did not take the bus.)
2. Tom would have helped us if he had known we were there.
   (What really happened was that he did not know we were there, and so he did not help us.)
3. If I had told Sarah the truth, I would have felt much better.
   (What really happened was that I did not tell Sarah the truth, and so I did not feel so good.)
4. If it hadn’t rained yesterday, we would have enjoyed a nice picnic.
   (What really happened was that it rained yesterday, and we did not go for a picnic.)

Note: You can use these modal verbs instead of would have: should have, could have, might have. Examples:

1. Jessica might have gotten the job if she had not been so nervous.
2. You could have arrived on time if you had used a map.
3. If she had known what to do, she should have told us.

Common Mistakes

1. Zero conditional (always true)
Structure: If/When + Simple Present + Simple Present
This type of conditional is almost always true and is in the simple present tense, meaning it can happen any time. Caution! The most common mistake is to use will in the main clause.

• Incorrect: When you leave the milk out, it will become sour.
  Correct: When you leave the milk out, it becomes sour.
• Incorrect: If it is cold inside, the heater will turn on.
  Correct: If it is cold inside, the heater turns on.

2. In the case of the second conditional, when the verb “to be” appears in the if clause, we can replace it with “were”.

• Incorrect: If I was you, I would not make such a mistake.
  Correct: If I were you, I would not make such a mistake.