“be able to”

be able to + 動詞原形——能夠做某事，有能力做某事。隨時態變化的只有 be（am / is / are, was / were, will be, have been…）；able to 和後面的動詞保持不變。

簡略回答重複 be / will / have：Yes, I was. / No, I won't. / No, I haven't. 否定也可以用 unable to（稍正式）：I'm unable to attend the meeting.

💡Able 是形容詞（和 tired、happy 一樣），所以前面一定要有 be——就像你說 I am tired 一樣。中文說“我能夠……”不需要別的詞，所以學習者常寫成 “I able to…” 或 “I don't able to…”。正確的形式是 I'm able to… / I'm not able to…

正如“‘can / could’ 表示能力”一課所講，can 只有兩種形式：can 和 could。其他情況都要用 be able to 代替 can。

1. 將來——will be able to / won't be able to

• After this course, you'll be able to order food in English.

  上完這門課，你就能用英語點餐了。

• Sorry, I won't be able to make it on Saturday.

  抱歉，星期六我去不了了。

如果是現在就安排或決定將來的事，用 can 仍然很自然：I can see you tomorrow at ten. 但如果這種能力現在還沒有，要以後才會有（上完課、身體好了、有了車……），就用 will be able to。

2. 完成時——have / has been able to

• I haven't been able to reach him all day.

  我一整天都聯絡不上他。

• Since she got glasses, she's been able to read the board clearly.

  她配了眼鏡以後，就能看清黑板了。

3. 在另一個情態動詞後面——might / may / should / must + be able to（兩個情態動詞不能連用）

• Ask Minh — he might be able to fix it.

  問問阿明吧——他也許能修好。（不說：might can）

• Nurses must be able to stay calm.

  護士必須能夠保持冷靜。

4. 在 to 後面和 -ing 形式中——to be able to, being able to

• I want to be able to talk to my customers in English.

  我希望能用英語和客戶交流。

• Being able to drive makes life much easier.

  會開車讓生活方便多了。

used to 也一樣：My grandpa used to be able to walk for hours.（他以前能走那麼久——現在不行了。）

在現在時中兩種說法都對，但口語裡 can 常用得多。Am / is / are able to 聽起來更正式——常見於郵件和通知——或者用來強調某人在情況變化後現在能夠做某事了。

• I can speak a little Japanese.

  我會說一點日語。（日常說法）

• Customers are able to change their booking online.

  顧客可以在網上更改預訂。（通知 / 正式）

• After the operation, Grandpa is able to walk again.

  手術後，爺爺又能走路了。（強調：他現在能走了）

• Minh could run really fast when he was a kid.

  阿明小時候跑得特別快。（一般能力）

• Yesterday Minh managed to catch the last train.

  昨天阿明趕上了末班火車。（某一次；不說：could catch）

• It was a tough match, but we were able to win.

  比賽很艱難，但我們還是贏了。

• The box was heavy, but I managed to carry it upstairs.

  箱子很重，但我還是把它搬上了樓。

Managed to + 動詞原形 強調這件事很難、費了一番力氣。否定：didn't manage to（= couldn't）。

例外：和 see、hear、smell、taste、feel、understand、remember 連用時，表示某一次也可以用 could：When I opened the door, I could smell smoke.

💡快速判斷：如果句子裡能加上 “in the end”（最後）或 “on that day”（那天），就是某一次 → was able to / managed to。如果你想說的是 “那時候我會……” → could。

• ✗I able to swim.

  ✓I'm able to swim.

  Able 是形容詞——需要 be。

• ✗We weren't able find the hotel.

  ✓We weren't able to find the hotel.

  able 後面總是跟 to。

• ✗I don't able to come.

  ✓I'm not able to come.

  否定用 be + not，不用 don't。

• ✗I hope I can be able to visit you.

  ✓I hope I'll be able to visit you.

  can 和 be able to 不能一起用。

• ✗The bus was late, but I could arrive on time.

  ✓The bus was late, but I managed to arrive on time.

  某一次具體的事 → 用 managed to / was able to，不用 could。

• ✗She has able to drive since last year.

  ✓She has been able to drive since last year.

  完成時：has been able to。