Conditional sentences are in the conditional mood (a sub-category of the subjunctive mood), which is used for hypothetical scenarios that are dependent on a certain condition or conditions. They are usually constructed using if to identify the conditions that must be met.
There are four “degrees” of conditionals, all of which vary in structure and meaning.
A zero conditional sentence uses the present simple tense to talk about what is always or generally true. It is classified as a conditional because it creates a hypothetical situation to describe what would be true each time something happens.
The general structure for the zero conditional is: “If + subject + present tense of predicate verb, subject + present tense of main verb.”
“If you throw a ball in the air, it comes back down.” (Always true: A ball comes back down every time you throw it in the air.)
“If we get up early, we always go jogging.” (Generally true: We jog every time we get up early.)
The first conditional is very similar in structure to the zero conditional. We still use if plus the present simple to create the condition, except that we now use the future simple tense (will + bare infinitive) to describe a probable result of the condition.
Thus, the structure is: “If + present simple tense, will + infinitive.”
- “If I see him, I will tell him.”
- “If I win the lottery, I will buy a new house.”
We can also create negative first conditionals by using the negative of the present simple in the if clause, and the negative of will in the future simple clause.
- “If I do not go, I will not see him.”
- “If I don’t see him, I won’t have to say goodbye.”
- “If he doesn’t arrive soon, we won’t have time to catch the 9:30 train.”
We can also reorder the sentence to have the future tense clause at the beginning of the sentence, and the if conditional clause at the end. Additionally, we can use modal auxiliary verbs other than will (such as must, can, could, may, might, or should) to create different shades of certainty in the future simple tense.
Let’s take a look at some examples:
- “I will go if he calls me.” (Will expresses a certainty.)
- “I must go if he calls me.” (Must expresses a personal obligation for the speaker.)
- “I can go if he calls me.” (Can expresses either permission from a third party or the fact that speaker is free from other commitments.)
- “I might go if he calls me.” (Might expresses a 50% possibility.)
- “I may go if he calls me.” (May is similar to might, but it is more formal and the possibility is slightly less.)
- “I should go if he calls me.” (The speaker feels a mild obligation.)
- “You should go if he calls you.” (The speaker is recommending that you go or is giving you a personal opinion.)
- “I can’t go if he calls me.” (The speaker is not able or does not have permission.)
- “I shouldn’t go if he calls me.” (The speaker feels a mild obligation not to.)
- “I might/may not go if he calls me.” (We very rarely contract might not in modern English, and we almost never contract may not.)
Interrogative sentences (questions)
To form a question in the first conditional, we invert the subject with the modal auxiliary verb.
- “If I he calls me, should I go?”
- “Could I leave early if Jake covers my shift?”
- “If I finish my homework on time, may I go to the party?”
- “If I come with you, will you buy me lunch?”
We use the second conditional to speak about a hypothetical situation or outcome resulting from the condition. Unlike the first conditional, we use the second conditional to talk about things that cannot or are unlikely to happen.
To create the second conditional, we use the past simple tense after the if clause, followed by would + the bare infinitive for the result of the condition.
In addition to would (which we use to describe something we would definitely do), we can also use could for what we would be able to do, as well as might for what it is possible (but unlikely) we would do.
- “If I went to London, I would visit Trafalgar Square.”
- “If I won the lottery, I could buy a new house.”
- “If you had a phone, you could call me every day.”
- “If I was/were* older, I might stay up all night long.”
(*Note that in more formal English, it is standard to use were in conditional sentences using the past tense of be, irrespective of it having a singular or plural subject. However, in everyday writing and speech, it is common to use was for singular subjects.)
We can also put the second conditional in the negative to describe something that would not be the case if something else were also not the case. To form the negative, we use the negative of the past simple in the if clause, and make would negative in the clause describing the result of the condition.
- “If our father didn’t work so hard, we wouldn’t be able to afford this house.”
- “If I didn’t live in London, I could never speak English so well.”
Interrogative sentences (questions)
To form questions in the second conditional, we invert would/could/might with the subject. For example:
- “If you had a million dollars, would you buy an expensive boat?”
- “Would you travel to South America if you spoke Spanish?”
We can also put a question word before would in this form:
- “What would you do if your family wasn’t so wealthy?”
- “Where might you go if you won the lottery?”
- “If you could have dinner with a famous person, who would you choose?”
Third conditionals are used to establish a hypothetical situation in the past, followed by a hypothetical outcome that did not really happen—typically, the outcome is the opposite of what actually happened.
(As with the second conditional, we can also use could or might instead of would. Additionally, we can use should have + the past participle to describe an outcome that ought to have happened.)
- “If I had been more prepared, I would have passed that test.”
In reality, the speaker was not prepared, and so they did not pass the test. By creating a condition in the past using the past perfect tense, they can articulate how they might have achieved a different outcome if they were more prepared.
Here are some other examples:
- Truth: “She was not there and couldn’t help you.”
- Conditional: “If she had been there, she could have helped you.”
- Truth: “I was late for work yesterday because I overslept.”
- Conditional: “If I hadn’t overslept, I wouldn’t have been late for work.”
- Truth: “You knew you had a test today.”
- Conditional: “If you knew you had a test today, you should have studied harder.”
Interrogative sentences (questions)
To form a question in the third conditional, we invert would/could/might/should with the subject and add a question word before it (if necessary).
- “Would you have come to the party if you had known about it?”
- “What might you have done if you had known the truth?”
- “Where could you have gone if you hadn’t come here?”
The Mixed Conditional
A very commonly used “fifth” conditional is what’s known as the mixed conditional, which is a cross between the third conditional and the second.
There are two ways to form a mixed conditional, depending on the meaning we wish to achieve.
If it is being used to describe how an unreal situation in the past might have affected an unreal outcome in the present, we use the past perfect tense in the if conditional clause and would / could + the bare infinitive of the verb for the result of the condition.
- “If I had studied more (the condition is in the past), I would be a doctor (the result of the condition is in the present).”
- “If I had been born in Italy, I would be Italian.”
- “If he hadn’t lost his job, he wouldn’t be unemployed.”
If the mixed conditional is being used to describe how an unreal condition in the present might have affected an unreal outcome in the past, we use the past simple tense in the if conditional clause and would have / could have + the past participle of the verb for the result of the condition.
- “If I wasn’t/weren’t so shy (condition in the present), I would have asked her on a date (unreal outcome in the past).”
- “If she was/were a better driver, she’d have gotten her license by now.”
- “If we worked a little harder, we could have finished this project already.”