The last post looked at the different kinds of subjunctive. The subjunctive mood of the verb is sometimes confused with conditional sentences. That may be because English can use the were subjunctive in a conditional sentence such as If I were you, I’d ask for your money back, where were expresses ‘unreal meaning’. This use of were is discussed more fully in the earlier post.
The main types of conditional sentence as taught to foreign learners are called the first, second and third conditional.
The first conditional is seen in a sentence such as If you run you will catch the train. The verb in the if clause is in the present tense, while the main clause has the modal verb will followed by the plain form of the main verb. This form of the conditional is used in situations where the action envisaged is quite likely to happen.
In the second conditional, events are far less certain. If we doubt the commitment and perhaps physical state of the person we’re talking to, we might say If you ran, you would catch the train. Here the verb in the if clause is in the past tense, while the main clause has would followed again by the plain form of the main verb. It can also occur more formally as If you were to run you would catch the train, and this can be inverted, without if, as Were you to run you would catch the train.
The third conditional is used in a situation where all hope of catching the train is lost, because it has left the station at the time of speaking. In those circumstances, we might say If you had run, you would have caught the train. To form that conditional sentence we use the past tense of have followed by the plain form of the main verb in the if clause. In the main clause we again use the modal verb would as in the second conditional, but follow it with have and the past participle of the main verb. This, too, can be inverted without if: Had you run, you would have caught the train.
This framework of three conditionals may be helpful to foreign learners, but more advanced students will want to know that it does not entirely reflect the reality, and that several other conditional sentences are also possible. One, sometimes known as the ‘zero conditional’, is used for a statement of what is generally believed to be a fact. For example, If water reaches 100 degrees, it boils. Here both verbs are in the present tense. Several other conditional sentences using combinations of verb phrases are also possible.