Conditional Sentences—Rules You Need to Know
- There are four types of conditional sentences.
- It’s important to use the correct structure for each of these different conditional sentences because they express varying meanings.
- Pay attention to verb tense when using different conditional modes.
- Use a comma after the if-clause when the if-clause precedes the main clause.
Conditional sentences are statements discussing known factors or hypothetical situations and their consequences. Complete conditional sentences contain a conditional clause (often referred to as the if-clause) and the consequence. Consider the following sentences:
What Are the Different Types of Conditional Sentences? There are four different types of conditional sentences in English. Each expresses a different degree of probability that a situation will occur or would have occurred under certain circumstances.
- Zero Conditional Sentences
- First Conditional Sentences
- Second Conditional Sentences
- Third Conditional Sentences
Let’s look at each of these different types of conditional sentences in more detail.
How to Use Zero Conditional Sentences
Zero conditional sentences express general truths—situations in which one thing always causes another. When you use a zero conditional, you’re talking about a general truth rather than a specific instance of something. Consider the following examples:
There are a couple of things to take note of in the above sentences in which the zero conditional is used. First, when using the zero conditional, the correct tense to use in both clauses is the simple present tense. A common mistake is to use the simple future tense.
Secondly, notice that the words if and when can be used interchangeably in these zero conditional sentences. This is because the outcome will always be the same, so it doesn’t matter “if” or “when” it happens.
How to Use First Conditional Sentences
First conditional sentences are used to express situations in which the outcome is likely (but not guaranteed) to happen in the future. Look at the examples below:
Note that we use the simple present tense in the if-clause and simple future tense in the main clause—that is, the clause that expresses the likely outcome. This is how we indicate that under a certain condition (as expressed in the if-clause), a specific result will likely happen in the future. Examine some of the common mistakes people make using the first conditional structure:
Explanation: Use the simple present tense in the if-clause.
Explanation: Use the zero conditional (i.e., simple present + simple present) only when a certain result is guaranteed. If the result is likely, use the first conditional (i.e., simple present + simple future).
How to Use Second Conditional Sentences
Second conditional sentences are useful for expressing outcomes that are completely unrealistic or will not likely happen in the future. Consider the examples below:
Notice the correct way to structure second conditional sentences is to use the simple past tense in the if-clause and an auxiliary modal verb (e.g., could, should, would, might) in the main clause (the one that expresses the unrealistic or unlikely outcome). The following sentences illustrate a couple of the common mistakes people make when using the second conditional:
Explanation: When applying the second conditional, use the simple past tense in the if-clause.
Explanation: Use a modal auxiliary verb in the main clause when using the second conditional mood to express the unlikelihood that the result will actually happen.
How to Use Third Conditional Sentences
Third conditional sentences are used to explain that present circumstances would be different if something different had happened in the past. Look at the following examples:
These sentences express a condition that was likely enough, but did not actually happen in the past. The speaker in the first sentence was capable of leaving early, but did not. Along these same lines, the speaker in the second sentence was capable of cleaning the house, but did not. These are all conditions that were likely, but regrettably did not happen.
Note that when using the third conditional, we use the past perfect (i.e., had + past participle) in the if-clause. The modal auxiliary (would, could, shoud, etc.) + have + past participle in the main clause expresses the theoretical situation that could have happened.
Consider these common mistakes when applying the third conditional:
Explanation: With third conditional sentences, do not use a modal auxiliary verb in the if-clause.
Explanation: The third conditional mood expresses a situation that could have only happened in the past if a certain condition had been met. That’s why we use the modal auxiliary verb + have + the past participle.
Exceptions and Special Cases When Using Conditional Sentences
As with most topics in the English language, conditional sentences often present special cases in which unique rules must be applied.
Use of the Simple Future in the If-Clause
Generally speaking, the simple future should be used only in the main clause. One exception is when the action in the if-clause will take place after the action in the main clause. For example, consider the following sentence:
The action in the if-clause is the aspirin easing the headache, which will take place only after the speaker takes them later that night.
“Were to” in the If-Clause
The verb phrase were to is sometimes used in conditional sentences when the likely or unlikely result is particularly awful or unthinkable. In this case, were to is used to place emphasis on this potential outcome. Consider these sentences:
Note that the emphatic “were to” can be used to describe hypothetical scenarios in the present, future, and past.
Punctuating Conditional Sentences
Despite the complex nature of conditional sentences, punctuating them properly is really simple!
Here’s the skinny:
Use a comma after the if-clause when the if-clause precedes the main clause.
If the main clause precedes the if-clause, no punctuation is necessary.