情態動詞 + have + V3

情態動詞 + have + 過去分詞 用來推測或評價一件已經發生的事。have 永遠不變——不管主語是什麼，都不用 has 或 had。

💡口語中 have 幾乎聽不見：must've /ˈmʌstəv/、should've、could've、might've——聽起來像 “must of”。書寫時一定要寫 have，而且 have 後面用過去分詞（gone、seen），不用一般過去時（went、saw）。

根據你有多確定來選擇情態動詞：

• Nobody's answering. They must have gone out.

  沒人接電話。他們一定是出去了。

• I may have left my wallet in the taxi.

  我可能把錢包落在出租車上了。

• Minh can't have written this — he doesn't speak French.

  這不可能是阿明寫的——他不會說法語。

• She couldn't have known about the party. We kept it secret.

  她不可能知道聚會的事。我們一直保密。

must have（表示推測時）的否定通常是 can't have / couldn't have。美式英語也常用 must not have + V3 表示“我肯定這事沒發生”（He must not have seen me），但縮寫 mustn't have 很少用。注意 couldn't have（不可能）比 might not have（也許沒有）語氣強得多。

同一個情態動詞：+ 動詞原形 說現在，+ have V3 說過去。見“推斷：must / can't”一課。

should have + V3 = 本該這樣做（但實際沒做）；shouldn't have + V3 = 本不該這樣做（但實際做了）。用來表示後悔或批評。ought to have 意思相同，但不太常用。should have 還可以表示“按理說現在應該已經……了”。

• We should have booked a table — the place is full.

  我們本該訂個位子的——店裡已經滿了。

• You shouldn't have said that to her.

  你不該對她說那種話。

• You ought to have asked before borrowing my bike.

  你借我腳踏車之前本該先問一聲。

• The parcel should have arrived by now.

  包裹按理說現在應該已經到了。（按預期）

• could have + V3：本來有可能，但沒有發生；也可以表示輕微的抱怨（You could have told me!）。
• couldn't have + 比較級：不可能更好 / 更糟了。
• would have + V3：你本來願意或準備去做，但被某事阻止了。
• needn't have + V3（主要是英式）：你做了，但其實沒必要。比較 didn't need to + 動詞：沒必要，所以（通常）你沒做。

• I could have gone to university, but I chose to work.

  我本來可以上大學，但我選擇了工作。

• You could have told me the meeting was cancelled!

  會議取消了你也不告訴我一聲！（輕微的抱怨）

• We couldn't have asked for better weather.

  天氣好得不能再好了。

• I would have called you, but my phone died.

  我本來會給你打電話的，但我手機沒電了。

• You needn't have cooked so much — there are only four of us.

  你其實不用做這麼多菜的——我們只有四個人。（你已經做了）

• I didn't need to cook — we ate out.

  我不用做飯——我們出去吃了。（所以我沒做飯）

• ✗She must has forgotten our meeting.

  ✓She must have forgotten our meeting.

  情態動詞後面永遠用 have。

• ✗You should have went to bed earlier.

  ✓You should have gone to bed earlier.

  have + 過去分詞，不用一般過去時。

• ✗I should of told you earlier.

  ✓I should have told you earlier.

  should've 聽起來像 “should of”，但其實是 have。

• ✗He can't have saw the message.

  ✓He can't have seen the message.

  can't have + 過去分詞。

• ✗She should have been arrived by now.

  ✓She should have arrived by now.

  arrive 是主動的——不需要 been。

• ✗I must have left my keys at home, but I'm not sure.

  ✓I might have left my keys at home, but I'm not sure.

  不確定 → might / may / could have。