Form In zero conditional sentences, the tense in both parts of the sentence is the simple present. If clause (condition) Main clause (result) If + simple present simple present If this thing happens that thing happens. As in all conditional sentences, the order of the clauses is not fixed. You may have to rearrange the pronouns and adjust punctuation when you change the order of the clauses, but the meaning is identical. In zero conditional sentences, you can replace "if" with "when", because both express general truths. The meaning will be unchanged. Examples If you heat ice, it melts. Ice melts if you heat it. When you heat ice, it melts. Ice melts when you heat it. If it rains, the grass gets wet. The grass gets wet if it rains. When it rains, the grass gets wet. The grass gets wet when it rains. Function The zero conditional is used to make statements about the real world, and often refers to general tru...