Conditional Sentences

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:
If you rest, you will feel better.
If you set your mind to a goal, you’ll eventually achieve it.
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:
If you will rest , you will feel better.
If you rest , you will feel better.
Explanation: Use the simple present tense in the if-clause.
If you set your mind to a goal, you eventually achieve it.
If you set your mind to a goal, you’ll eventually achieve it.
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:
If I inherited a billion dollars, I would travel to the moon.
If I owned a zoo, I might let people interact with the animals more.
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:
If I inherit a billion dollars, I would travel to the moon.
If I inherited a billion dollars, I would travel to the moon.
Explanation: When applying the second conditional, use the simple past tense in the if-clause.
If I owned a zoo, I will let people interact with the animals more.
If I owned a zoo, I might let people interact with the animals more.
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.