同学你好，该知识点来自沪江网校《新概念英语第三册【随到随学班】》的课程，想要更系统的学习，欢迎进入课程学习。不仅可以和更多的同学一起学习，而且还有老师、助教随时的学习指导和知识点解答哦。

同学好：
非真实条件句描述的条件则几乎不可能发生，多是与事实相反的假设，主句的动作也是不可能发生的事实。

非真实条件句则通常有三种比较固定的句式。
与现在事实相反的虚拟：
从句谓语用动词过去式(be 用 were)；主句谓语用would / should / might / could + 动词原形。
If he were free, he would help us.
要是他有空的话，他会帮助我们的。

与过去事实相反的虚拟：
从句谓语用had +动词过去分词；主句谓语用would / should / might / could have + 动词过去分词。
If I had got there earlier, I would have met Mr. Li.
如果我早点到那儿，我就会见到李先生了。

与将来事实相反的虚拟：
从句谓语用 动词过去式(be用were)/  should + 动词原形/  were to + 动词原形；主句谓语用would / should / might / could + 动词原形。
If he were to come here, he would tell us about it.
如果他要来的话，他会通知我们一声。

希望对同学有帮助～

祝学习愉快！