As is typical for many languages, full conditional sentences in English consist of a conditional clause or protasis specifying a condition or hypothesis, and a consequence clause or apodosis specifying what follows from that condition. The condition clause is a dependent clause, most commonly headed by the conjunction if, while the consequence is contained in the main clause of the sentence. Either clause may appear first.
Different types of conditional sentences (depending largely on whether they refer to past, present or future time frame) require the use of particular verb forms (tenses and moods) to express the condition and the consequence. In English language teaching the most common patterns are referred to as first conditional, second conditional and third conditional; there is also a zero conditional and mixed conditional.
216 If he comes to me tomorrow, we will eat lunch together.
217 If he came to me tomorrow, we would eat lunch together.
218 If she were (was) my daughter, we would eat lunch together.
219 If she had come to me yesterday, we would have eaten lunch together.
220 If I had time, we would eat lunch together.
If I had had time, we would have eaten lunch together.
221 I don’t have enough money. If I had the money, I would buy the car. I don’t have enough money otherwise, I would buy the car.
222 I didn’t have enough money. If I had had the money, I would have bought the car. I didn’t have enough money otherwise, I would have bought the car.
