语法为表达服务。
现在完成式（Present Perfect Tense）
| Just | Yet | Still | Already | |
|---|---|---|---|---|
| 意思 | 刚刚、刚好、刚才 | 还未完成 | 原本预计内应该要完成，但还未完成 | 已经完成，比预期内提早完成 |
| 位置 | 放在助动词 Have 与动词之间 | 句末 | 句中 | 放在助动词 Have 与动词之间 |
| 语气 | – | 中立 | 批判 | – |
| 否定型 | – | ✓ | ✓ | – |
| 例句 | I have just handed in my homework. (我刚刚递交了功课。) | I have not yet handed in my homework. (我还未递交功课。) (暗藏意味：尚未完成某些事，也不知道什么时候会完成，时间点比较模糊) | I still have not handed in my homework. (我仍然未递交功课。) (暗藏意味：期限已经过了，但是我还是没有交功课。) | I have already handed in my homework. (我已经递交了功课。) (暗藏意味：我在限期前交了功课。) |
不定式
表结果
- I hurried to the railway station to find my train is gone.
✔️ 我匆忙地赶到火车站（结果）却发现我的车已经出发了。
❌ 我匆忙地赶到火车站，是为了发现我的车已经走了（目的）。 - 🌰 A Pittsburgh-area woman with car trouble popped the hood of her vehicle to find squirrels had hidden more than 200 walnuts in the car's body.
- 🌰 He survived to see the end of the war.
虚拟语气
英语分 3 种语气：
陈述语气：陈述事实、提出看法或问题等。所说的是真的。
I like this book the best.
If you get up earlier, you will be able to catch the first bus.祈使语气：表示请求、命令或警告等。希望所说的成真。
Don’t be so careless.虚拟语气：表示假想或主观愿望。所说的与事实不符。
I suggest that we should go tomorrow.
If you dropped the glass, it would break.
How to 虚拟语气：
- 以动词的过去式作为表达「非事实」的手段。
- 过去式并不是过去时。虚拟语气中的过去式只是一个表示虚拟语气的形式，而不是表示过去的时态的形式。
虚拟现在
- 条件从句的谓语：用过去式（be 用 were）
- 主句谓语：should / would / could / might + 动词原形
e.g. (example given)
- If I were you, I would not tell him the truth.
- If we left now, we should arrive in good time.
虚拟过去
因为时间本来就是过去，若还要用过去形态来表达非事实语气，就必须用过去完成的形态。
- 条件从句的谓语：had+ 过去分词
- 主句谓语：should / would / could / might + have+ 过去分词
e.g.
- If you had got up earlier, you would have caught the first bus.
- If he had been in that train then, he might have been killed in that accident.
虚拟将来
- 条件从句的谓语：用过去式（be 用 were）
- 主句谓语：should / would / could / might + 动词原形
e.g.
- If he went, would you go too.
- If I asked him, I'm sure he'd help us.
- 可能性特别低：should
If I should win the lottery, I would buy you a car. - 不可能发生：were to
If I were to lie to her, I would lose her.
Tips
倒装结构
If I were a boy, I might be very handsome.
Were I a boy, I might be very handsome.
be 动词因虚拟语气变为过去式时只会变为 were，而永远不会变成 was。
混合时态会有一个明显的时间标识，例如 now
If I had finished my work earlier, I could have dinner now.
If you'd listened to me, you wouldn't be in such trouble now.混合语气
I could have caught that bus, only that I forgot to get any money out.
特殊结构
- She was the only person to survive the air crash.
