1. used to express inability or impossibility in the past
用於表示過去的能力不足或不可能性
I couldn't open the door because it was locked.
我打不開門，因為門鎖著。
She couldn't come to the party yesterday.
她昨天無法來參加派對。
Couldn't Meaning（定義、用法、例句與發音）
couldn't
modal
快速理解
What does "Couldn't" mean?What are 2-3 core uses of "Couldn't"?
couldn't 是 could not 的縮寫，主要表達過去的能力不足、可能性極低或禮貌的請求與建議。
- 1
過去的能力不足
EN: I couldn't solve the math problem yesterday.
翻譯: 我昨天解不出那道數學題。
- 2
推測可能性極低
EN: That couldn't be true.
翻譯: 那不可能是真的。
- 3
禮貌的請求或建議
EN: Couldn't you help me for a moment?
翻譯: 你能不能幫我一下？
- 4
與感官動詞連用，描述過去持續的狀態
EN: I couldn't believe my eyes.
翻譯: 我當時簡直不敢相信自己的眼睛。
小提醒：注意：couldn't 用於過去「單次」無法做到某事時，在肯定句中通常用 was/were not able to 或 managed to 來表達「成功做到」，而非 could。
發音（How to Pronounce "Couldn't" in English）
How to pronounce "Couldn't" in English?"Couldn't" US vs UK pronunciation
點擊下方的 US / UK 按鈕可播放發音。
Real-life Examples of "Couldn't" from YouTube Videos
South Korea would accept Trump-Kim deal to freeze North Korea’s nuclear programme | BBC News
BBC News
“So last time Trump was president, he met with Kim Jong-un three times and the pair of them had these big talks over trying to get North Korea to give up its nuclear weapons in return for relieving sanctions on the North Um, and the US was asking the North to dismantle some of its nuclear facilities, but in the end the pair just couldn't reach an agreement.”
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Definitions（定義）
What are the definitions of "Couldn't"?How does "Couldn't" change by context?
2. used to express that something was not possible or did not happen
用於表示某事過去不可能或沒有發生
We couldn't find a parking space anywhere.
我們到處都找不到停車位。
He couldn't remember her name.
他想不起她的名字。
3. used in polite requests or suggestions, often with 'you'
用於禮貌的請求或建議，常與 'you' 連用
Couldn't you help me with this for a moment?
你能不能幫我一下這個？
Couldn't we try a different approach?
我們能不能試試不同的方法？
4. used with comparative adjectives to emphasize a strong feeling or opinion
與比較級形容詞連用，以強調強烈的感受或意見
I couldn't be happier with the results.
我對結果再滿意不過了。
The weather couldn't be better for a picnic.
這天氣對野餐來說再好不過了。
Grammar & Patterns（句型）
What are common sentence patterns for "Couldn't"?How to make natural sentences with "Couldn't"?
| Pattern | Meaning | Example |
|---|---|---|
| couldn't + V (base form) | 表示過去沒有能力做某事 | I couldn't open the door. (我當時打不開門。) |
| couldn't + have + past participle | 表示對過去可能性的推測（否定）或過去不可能發生的事 | She couldn't have known the truth. (她當時不可能知道真相。) |
| couldn't + be + comparative adjective | 用於強調，表示「再…不過了」 | The news couldn't be better! (這消息再好不過了！) |
| couldn't help + V-ing | 表示忍不住、無法不做某事 | I couldn't help laughing. (我忍不住笑了出來。) |
| couldn't + see/hear/understand + noun/wh-clause | 表示過去無法看見、聽見或理解 | We couldn't see what was happening. (我們看不到當時發生了什麼事。) |
用法說明
How is "Couldn't" different from similar structures?What usage mistakes are common with "Couldn't"?
couldn't have done vs. couldn't do
- couldn't have done 用於推測或評論過去「不可能發生」或「不可能做到」的事情，強調對過去情況的判斷。
- couldn't do 則描述過去「沒有能力做」或「無法做到」某事的單純事實，通常指具體情境下的能力或可能性缺失。
- 兩者都談論過去，但 couldn't have done 的推測語氣更強，常與虛擬語氣或條件句連用。
對比例句： EN: She couldn't have finished the report by herself; it's too complex. 翻譯: 她不可能自己完成那份報告；那太複雜了。
EN:She couldn't finish the report yesterday because her computer crashed.
翻譯:她昨天無法完成報告，因為她的電腦當機了。
對比例句： EN: They couldn't have known about the surprise party. 翻譯: 他們當時不可能知道驚喜派對的事。
EN:They couldn't know the answer without studying.
翻譯:他們不學習就無法知道答案。
總結建議
當想表達對過去事件的推測或假設性否定時，使用「couldn't have + 過去分詞」；若僅陳述過去事實上的「無法做到」，則使用「couldn't + 動詞原形」。
易混淆對比
What is the difference between "Couldn't" and similar words?How to choose "Couldn't" vs alternatives?
couldn't vs could not
「couldn't」是「could not」的縮寫形式，兩者意義與用法完全相同，僅有正式程度的差別。
couldn't vs wasn't/weren't able to
「couldn't」與「wasn't/weren't able to」皆可表示過去「無法做到」某事，但後者更強調在特定情境下「能力或機會的缺乏」。
couldn't vs wouldn't
「couldn't」表示「沒有能力或可能性」做某事；「wouldn't」則表示「不願意」或「拒絕」做某事。
口語用法
How is "Couldn't" used in spoken English?What is the spoken vs formal difference for "Couldn't"?
引述
在口語中，常用來轉述他人或自己過去的想法、說法或可能性。 EN: She said she couldn't make it to the party. 翻譯: 她說她沒辦法來參加派對。
EN:I thought I couldn't finish the work on time, but I did.
翻譯:我本來以為我沒辦法準時完成工作，但我做到了。
語氣強調
用來強調「無法做到」的無奈感或加強否定的語氣，常伴隨特定的語調。 EN: I just couldn't believe my eyes when I saw it. 翻譯: 我看到的時候，簡直不敢相信自己的眼睛。
EN:We tried everything, but we simply couldn't fix it.
翻譯:我們什麼方法都試過了，但就是修不好。
停頓填充
在思考或組織語句時，作為一種口語填充，常用於「I couldn't... you know...」或「I couldn't — well, it was hard」這類結構中。 EN: His reaction was... I couldn't... really describe it properly. 翻譯: 他的反應是... 我沒辦法... 真的好好形容。
EN:It was a situation where I couldn't — you know what I mean — just walk away.
翻譯:那是一種我沒辦法——你懂我的意思——就這樣走開的情況。
正式寫作注意：在正式或學術寫作中，應避免使用帶有縮寫的「couldn't」，須改為完整的「could not」。口語中常見的停頓填充用法也應避免，以保持文句的簡潔與嚴謹。
常見短語
What common collocations use "Couldn't"?What fixed phrases with "Couldn't" should I remember?
couldn't help
couldn't help (but) + verb-ing / couldn't help + noun/pronoun
忍不住，無法控制地做某事
couldn't care less
couldn't care less (about something)
毫不在乎，一點也不關心
couldn't be bothered
couldn't be bothered (to do something)
懶得（做某事），嫌麻煩而不願做
couldn't agree more
couldn't agree more (with someone/something)
完全同意，再同意不過了
couldn't believe
couldn't believe (it/one's eyes/ears)
無法相信，感到難以置信
couldn't wait
couldn't wait (for something / to do something)
迫不及待，等不及
couldn't stand
couldn't stand (someone/something / doing something)
無法忍受，受不了
couldn't have been
couldn't have been + comparative adjective / couldn't have + past participle
（過去）不可能…；不可能比…更…了
常見錯誤
What are common mistakes with "Couldn't"?Which "Couldn't" sentences look correct but are wrong?
×I couldn't to finish my homework.
✓I couldn't finish my homework.
「couldn't」是情態動詞，後面直接接動詞原形，不加「to」。
×If I studied harder, I couldn't fail the exam.
✓If I studied harder, I wouldn't fail the exam.
在假設語氣（第二條件句）中，表示「不會」發生某事，應用「wouldn't」。「couldn't」表示「沒有能力」或「不可能」，不適用於此種假設結果。
×I couldn't saw him yesterday.
✓I couldn't see him yesterday.
情態動詞「couldn't」後的動詞必須是原形，不能使用過去式。動詞的過去時態已由「couldn't」本身表達。
×This couldn't be true! (當表達現在或未來極不可能時)
✓This can't be true!
對現在或未來情況表示強烈懷疑或認為「不可能」時，應用「can't」。「Couldn't」用於過去的能力或可能性，或用於比「can't」更委婉地表示現在的不可能（尤其在條件句中）。在表達震驚、不相信的驚嘆句中，多用「can't」。
×I couldn't buy the car because it is too expensive.
✓I can't buy the car because it is too expensive.
描述現在因為某個（持續的）原因而「不能」做某事，應用「can't」。「Couldn't」通常用於描述過去某個特定時間或情境下沒能做到的事。
×Couldn't you help me tomorrow?
✓Can you help me tomorrow? / Could you help me tomorrow?
「Couldn't you...?」用於表達驚訝、責備或強烈的建議（意為「你難道不能...嗎？」），語氣較強。單純、禮貌地詢問未來的能力或可能性時，應用「Can you...?」或更委婉的「Could you...?」。
詞形變化
What are the word forms of "Couldn't"?What are tense/participle forms of "Couldn't"?