虚拟语句的三种形式主要分为与现在、过去、将来事实相反的虚拟条件句，具体如下：

一、与现在事实相反的虚拟

结构：If + 主语 + 动词过去式（be动词用were），主句 + would/should/might/could + 动词原形

例句：If I were you, I would take the chance.（如果我是你，我会抓住这个机会。）

二、与过去事实相反的虚拟

结构：If + 主语 + had + 过去分词，主句 + would/should/might/could + have + 过去分词

例句：If I had known the truth, I would have told you.（如果我知道了真相，我会告诉你的。）

三、与将来事实相反的虚拟

结构一：

If + should + 动词原形，主句 + would + 动词原形

- 例句：If it should rain tomorrow, we would stay at home.（如果明天下雨，我们会待在家里。）

结构二：

If + 主语 + were to + 动词原形，主句 + would + 动词原形

- 例句：If there were a heavy snow next Sunday, we would go skating.（如果下周日下大雪，我们就去滑冰。）

结构三：

If + 主语 + 动词过去式（be动词用were），主句 + would + 动词原形

- 例句：If the sun were to rise in the west, we would lend you money.（如果太阳从西边升起，我们就会借给你钱。）

补充说明：

虚拟条件句中，从句可省略if，但需部分倒装（如were to do）；

含蓄虚拟语气常通过without/but for等词汇表达，与虚拟条件句等价。