could

could — 情態動詞

1. used when talking about what a person or thing was able to do on a particular oc

1.情態動詞A1
釋義

能夠；可以

過去有能力或機會做某事

used when talking about what a person or thing was able to do on a particular occasion in the past, or about a skill or natural ability someone had before now

例句

When I was six, I could already read simple storybooks by myself.

我六歲時就已經能自己讀簡單的故事書了。

The swimmer could hold her breath for nearly two minutes.

那位游泳選手能閉氣將近兩分鐘。

同義詞
  • was able to

    more formal; also used for single past achievements where 'could' may sound unnatural

  • managed to

    emphasises effort or difficulty overcome in a specific situation

反義詞

文法句型

could + base form (affirmative)

could not / couldn't + base form (negative)

could + subject + base form? (question)

用法筆記

For the present tense, use 'can' instead of 'could'. In affirmative sentences about a single past achievement ('managed to'), 'was/were able to' is more common than 'could'.

常見錯誤

❌Yesterday I can swim across the lake.
✅Yesterday I could swim across the lake.
💡Use 'could' (not 'can') for past ability.
❌He could to run fast when he was young.
✅He could run fast when he was young.
💡Do not add 'to' after a modal verb.

2. used as a polite way to ask for permission to do something — softer and more hes

2.情態動詞A1
釋義

可以

客氣地請求允許

used as a polite way to ask for permission to do something — softer and more hesitant than 'can', which some listeners may find too direct

例句

Could I open the window? It feels a bit stuffy in here.

我可以開窗戶嗎？這裡有點悶。

polite request for permission: Could I + verb

Could we leave a little earlier today? I have a doctor's appointment.

我們可以早一點離開嗎？我預約了看醫生。

同義詞
  • can

    less polite, used in informal situations

  • may

    more formal, common in official or written contexts

文法句型

Could + I/we + base form? (asking for permission)

Could + I/we + possibly + base form? (more hesitant)

用法筆記

This sense always appears in question form. 'Could' is more polite than 'can', while 'may' is slightly more formal. In spoken English, 'Can I…?' is also acceptable but less courteous.

常見錯誤

❌Could I to borrow your pen?
✅Could I borrow your pen?
💡Do not add 'to' after a modal verb.

3. used as a courteous way of asking another person to take a particular action — s

3.情態動詞A1
釋義

能不能

客氣地請對方做某事

used as a courteous way of asking another person to take a particular action — softer in tone than the more direct 'can'

例句

Could you please pass me the salt? I can barely reach it.

可以請你把鹽遞給我嗎？我幾乎構不到。

Could you please + verb (standard polite request)

Could you help me move this table to the other side of the room?

你能幫我把這張桌子搬到房間的另一邊嗎？

同義詞
  • can

    less polite; sounds more like an instruction than a request

  • would

    similar politeness level; 'would you' can sound slightly more hypothetical

文法句型

Could + you + please + base form? (polite request)

Could + you + possibly + base form? (more hesitant request)

用法筆記

Like sense 2, this always takes question form. The addressee is almost always 'you'. Adding 'please' makes the request warmer. To sound even more hesitant or apologetic, use 'Could you possibly…?'

常見錯誤

❌Could you to open the door?
✅Could you open the door?
💡Never insert 'to' between a modal and the main verb.

❌ 'Could you give me a hand?' (acceptable) — This is actually fine; just avoid 'to'.

4. used to say that something is possible or might happen, especially when you are

4.情態動詞A2
釋義

可能；也許

表示不確定的可能性

used to say that something is possible or might happen, especially when you are not certain or when the chance is not strong

例句

The traffic could be really bad on a Friday afternoon.

星期五下午的交通可能會非常擁擠。

Don't throw that box away — it could be useful for storage.

別把那個箱子丟掉——它可能可以用來收納東西。

possibility: could + be + adjective

同義詞
  • might

    similar level of possibility; often interchangeable with 'could'

  • may

    slightly more formal and can imply a marginally higher chance

  • can

    used for general possibility; 'could' sounds more tentative about a specific case

反義詞

文法句型

could + base form (present/future possibility)

could + have + past participle (past possibility that did not happen)

could + be + -ing (present possibility)

用法筆記

To express a stronger degree of certainty, use 'may' or 'might'. 'Could' suggests a real but not confidently expected possibility. For past possibilities that did not actually happen, use 'could have + past participle': 'You could have hurt yourself.'

常見錯誤

❌It could rains tomorrow.
✅It could rain tomorrow.
💡After a modal verb, use the base form of the main verb, not an -s form.

5. used to make a suggestion or offer an idea about what someone might do, either f

5.情態動詞A2
釋義

可以；不妨

提出建議或想法

used to make a suggestion or offer an idea about what someone might do, either for their own benefit or as a shared plan

例句

You could try calling her again later this evening.

你可以試試今晚晚一點再打電話給她。

suggestion: you could + try + -ing

We could take the scenic route along the coast instead of the highway.

我們可以沿著海岸走風景優美的路線，不開高速公路。

同義詞
  • might

    in suggestion contexts, 'might' sounds slightly more formal: 'You might want to try…'

  • should

    stronger and more directive; suggests a moral obligation or strong recommendation

文法句型

You/We could + base form (suggestion)

We could always + base form (alternative suggestion)

You could try + -ing / noun (suggestion with try)

用法筆記

Unlike sense 4 (POSSIBILITY), this sense offers a course of action the listener could choose. In questions ('Could we…?'), it overlaps with making a tentative suggestion. To make the suggestion stronger or more definite, use 'should' or 'ought to'.

常見錯誤

❌You could to try the new restaurant.
✅You could try the new restaurant.
💡Never add 'to' after 'could'.

6. expressing irritation or disappointment that a person failed to carry out an act

6.情態動詞B1
釋義

本來可以

責怪對方未做該做的事

expressing irritation or disappointment that a person failed to carry out an action the speaker believes was reasonably expected of them

例句

You could have told me you were not coming to the party.

你本來可以告訴我你不來參加派對的。

could have + past participle for past criticism

João could have asked before borrowing his brother's car.

João 在借用哥哥的車之前本來可以先問一聲的。

同義詞
  • should have

    stronger sense of duty or moral obligation; 'could have' focuses on missed opportunity or reasonable expectation

文法句型

could + have + past participle (criticism about a past inaction)

could + at least + have + past participle (emphasising minimum expected action)

用法筆記

This sense almost always uses 'could have + past participle' referring to a past action that the speaker believes was expected. In speech, 'could have' is usually contracted to 'could've' (/ˈkʊd.əv/). The tone ranges from mild disappointment to strong anger depending on intonation.

常見錯誤

❌You could of told me earlier.
✅You could have told me earlier.
💡'Could of' is a common misspelling of the contracted form 'could've'. Never write 'of' after 'could'.