虚拟语气是高中语法的难点，难在「形式倒退」：说现在的事用过去式，说过去的事用过去完成时。学生最容易按真实条件句直译，一步走错整句崩。三种基本句型各一张结构表，套公式即可。
if 虚拟条件句三型对照表
| 类型 | if 从句 | 主句 | 例句 |
|---|---|---|---|
| 与现在事实相反 | did / were | would + 原形 | If I were you, I would accept the offer. |
| 与过去事实相反 | had + 过去分词 | would have + 过去分词 | If he had studied harder, he would have passed. |
| 与将来事实相反 | did / should + 原形 / were to do | would + 原形 | If it rained tomorrow, we would stay at home. |
wish 后的虚拟与固定句型
- wish + 过去式：与现在相反的愿望——I wish I were a bird.
- wish + had done：与过去相反的遗憾——I wish I had gone to the party.
- would rather + 过去式：宁愿——I would rather you came tomorrow.
- It is high time that + 过去式：该是……的时候了
- as if / as though 后按实际情况选虚拟或陈述
判断第一步永远是分清「真实还是虚拟」：If it rains tomorrow, we will stay at home 是真实条件（雨可能下）；If it rained tomorrow, we would stay at home 是虚拟（雨下的可能性小）。语气一变，时态全变。
易错点：与现在相反的虚拟里 be 一律用 were
虚拟语气中第一、第三人称单数也不用 was：If I were you、If he were here，书面语和考试都以 were 为准。另一个高频考点是 if 省略后的倒装：Were I you、Had he come earlier、Should it rain tomorrow——把 were、had、should 提前。判断方法看句首：没有 if 但句首出现这三个词加主语的倒装语序，就是省略 if 的虚拟句。真实条件与虚拟条件混在一起出题时，先看从句动词退没退时态，退了按虚拟套公式，没退按主将从现走。