This document discusses the different types of conditional sentences in English. There are three types of conditional sentences: Type I are possible to fulfill, Type II are theoretically possible, and Type III are not possible. Type I uses present tense in the if-clause and will or may in the main clause. Type II uses past tense in the if-clause and would in the main clause. Type III uses past perfect in the if-clause and would have in the main clause. Examples are provided of conditional sentences with the if-clause at the beginning or end of the sentence. Affirmative and negative examples are also given for each type.