Conditionals

Conditional sentences usually consist of a subordinate if-clause and a main clause. The order of the clauses is optional, but if the if-clause is first, a comma is used to separate the two clauses:

You might have been accepted if you had applied earlier.
If you had applied earlier, you might have been accepted.

If the if-clause is first, we can use then in the main clause:

If you had applied earlier, then you might have been accepted.

The different types of conditionals, which are discussed in the following chapters, may refer to different times (future, present, past) and express different degrees of reality. The choice of verb forms used in conditionals depends on whether the condition is true, probable or unreal.

If the condition is true or probable, we use real tenses:

If you missed the 6 o'clock train, you won't get here before 7. (the condition is true: you missed the train; here missed refers to the past and won't get to future time)

If you miss the 6 o'clock train, you won't get here before 7. (the condition is probable: you may miss the train; here miss and won't get refer to future time)

If the condition is unreal, we use unreal tenses:

If you missed the 6 o'clock train, you wouldn't get here before 7. (the condition is unreal or improbable: you probably won't miss the train; here the past subjunctive form missed and wouldn't get refer to future time)

If you had missed the 6 o'clock train, you wouldn't have got here before 7. (the condition is unreal: you didn't miss the train; here the past perfect subjunctive form had missed and wouldn't have got refer to past time)