最核心的 3 种表达方式
一、用「条件句 if + 非真实时态」
对现在不真实
If I were rich, I would travel the world.
- 现实：我不富
- 形式：if + 过去式 / were
- 主句：would + 动词原形
信号词：
- were（不管主语是谁）
- would / could / might
对过去不真实（最常见的后悔）
If I had known, I would have told you.
- 现实：我不知道
- 形式：
- if 从句：had + 过去分词
- 主句：would have + 过去分词
信号词：
- had done
- would have done
对将来不太可能
If he should call, tell him I’m out.
- should + 动词原形
- 偏正式
二、用情态助动词表示“虚拟”
即使没有 if，也可以是虚拟语气。
would / could / might
I would help you, but I’m busy.
I could have done better.
判断技巧：
- would + 现在 → 假设
- would have + 过去 → 后悔 / 本可
三、用「wish / if only / would rather」句型
wish（对现实不满）
| 想表达 | 形式 |
|---|---|
| 现在 | wish + 过去式 |
| 过去 | wish + had + 过去分词 |
| 将来 | wish + would |
例子：
I wish I knew the answer.
I wish I had studied harder.
if only（情绪更强）
If only I had listened to you!
（要是当初听你的就好了！）
would rather / it’s time
I’d rather you left now.
It’s time we went home.
用过去式，表示“现在该做却没做”。
固定触发「虚拟语气」的动词 / 句型
表建议、要求、命令
suggest / demand / insist / recommend
结构：
动词 + (that) + 主语 + 动词原形
例子：
I suggest that he go now.
She insisted that he be present.
注意：不是过去，是“原形”
固定结构
- as if / as though
He talks as if he knew everything.
（实际上不知道）
条件句倒装的总规则
当 if 从句里出现 had / were / should 时，可以把 if 去掉，把 had / were / should 提到句首
公式：
if + 主语 + had / were / should + … ↓ had / were / should + 主语 + …
三种最重要的倒装模板
一、Had + 主语 + 过去分词
（过去不真实）
原句
If I had known, I would have told you.
倒装
Had I known, I would have told you.
用途：
- 第三条件句
- 表后悔 / 反事实
二、Were + 主语 + 补语
（现在不真实）
原句
If I were you, I would leave.
倒装
Were I you, I would leave.
特点：
- 只能用 were
- 非常正式 / 文学感
三、Should + 主语 + 动词原形
（将来不确定 / 万一）
原句
If he should call, tell him I’m out.
倒装
Should he call, tell him I’m out.
用途：
- 通知
- 规章
- 公告