must

must — 情態動詞

1. Describes a situation where a rule, a law, or a practical need requires somethin

1.情態動詞A2
釋義

必須

表示因規則或實際需求而有義務

Describes a situation where a rule, a law, or a practical need requires something — for example, fastening a seatbelt because the law demands it, or sending a form before a closing date.

例句

All passengers must fasten their seat belts during takeoff and landing.

所有乘客在起飛和降落時必須繫好安全帶。

must + base verb — rule or law obligation

Felix must finish his homework before he can watch television.

Felix 必須先做完功課才能看電視。

同義詞
  • have to

    more common in everyday speech for describing obligations; works in all tenses

  • need to

    slightly weaker than 'must', focuses on what is necessary rather than what is required by rule

  • be required to

    more formal; common in official notices and regulations

反義詞
  • must not

    the direct negative — forbids the action

  • do not have to

    indicates that something is not necessary, not that it is forbidden

文法句型

must + base verb

must not + base verb (prohibition)

must + be + past participle (passive obligation)

用法筆記

Must has no past-tense form. For past obligation, use 'had to' (e.g., 'I had to leave early yesterday'). For prohibition in the past, use 'was / were not allowed to' (e.g., 'We were not allowed to park there'). Must is also not used with 'do/does/did' in questions or negatives — the negative is must not (contracted mustn't).

常見錯誤

❌I must go to the store yesterday.
✅I had to go to the store yesterday.
💡'must' has no past tense; use 'had to' for past obligation.
❌You must not go to the party if you do not want to.
✅You do not have to go to the party if you do not want to.
💡'must not' means it is forbidden, not merely unnecessary; use 'do not have to' for optional things.

2. used to show that you have made a strong decision to do something and will not l

2.情態動詞B1
釋義

一定要；非得

表示下定決心要做某事

used to show that you have made a strong decision to do something and will not let anything stop you — for example, promising yourself to quit smoking or to save money each month.

例句

I must call my grandmother more often — I keep forgetting.

我一定要更常打電話給奶奶——我老是忘記。

must + base verb — self-imposed personal intention

Christopher must stop staying up so late or his health will suffer.

Christopher 非得戒掉熬夜的習慣，否則他的健康會出問題。

同義詞
  • have got to

    more informal; common in British English for personal intentions

  • be determined to

    conveys the same strong resolve but works in all tenses

  • will

    less forceful; a simple statement of future action rather than a strong intention

文法句型

must + base verb

用法筆記

This sense expresses a personal resolve, not an external obligation. For past intentions, use 'was determined to' (e.g., 'I was determined to finish the marathon').

3. used before a verb to make your statement feel more forceful or emotionally char

3.情態動詞B1
釋義

非得；就是

加強語氣以表達強烈情緒或堅持

used before a verb to make your statement feel more forceful or emotionally charged — for example, insisting that something is true, expressing surprise, or adding weight to an opinion.

例句

I must say, I am really impressed by your presentation.

我必須說，你的簡報真的讓我印象深刻。

must say — fixed emphatic phrase for emotional force

I must admit, I was completely wrong about the election result.

我必須承認，我對選舉結果的看法完全錯了。

must admit / must say — fixed emphatic phrase

同義詞
  • really

    adverb that can add similar force: 'You really should see the sunset'

  • simply must

    more emphatic version of 'must'

文法句型

must + base verb

must admit / must say

must + be + complement

用法筆記

Distinguish from sense 5 (LOGICAL DEDUCTION): in this emphasis sense, 'must' adds emotional force to a statement the speaker already knows to be true, rather than drawing a conclusion from evidence. Common fixed phrases include 'I must say', 'I must admit', and 'you must know'.

4. used to tell someone that you strongly believe they will enjoy or benefit from s

4.情態動詞A2
釋義

一定要；應該

熱情推薦某人做開心的事

used to tell someone that you strongly believe they will enjoy or benefit from something — for example, suggesting a film, a restaurant, or an experience with enthusiasm.

例句

You must try the chocolate cake at that little café downtown.

你一定要試試市中心那家小咖啡店的巧克力蛋糕。

must + base verb — enthusiastic suggestion

Adina told me, 'You must read this novel — you will love it.'

Adina 跟我說：「你一定要讀這本小說——你會愛上它的。」

同義詞
  • should

    less forceful than 'must'; a gentle suggestion rather than an enthusiastic recommendation

  • have to

    usually implies obligation, not recommendation; less suitable for enthusiastic suggestions

  • ought to

    similar to 'should' in strength; slightly more formal

文法句型

must + base verb

用法筆記

This sense is only used in the second person ('you must...') or reported speech about a recommendation ('She said I must...'). Unlike sense 1 (NECESSITY), there is no external rule — the speaker is simply expressing personal enthusiasm.

常見錯誤

❌You must go to the museum — it is required for the class.' (if the speaker means a class requirement, not a recommendation).
✅You must go to the museum
💡it is fantastic.' — For requirements, the context should clearly show a rule; for enthusiastic suggestions, the context should show personal enjoyment.

5. Expresses near-certainty based on clear evidence — for example, hearing a doorbe

5.情態動詞B1
釋義

一定是；想必

根據證據推斷某事很可能屬實

Expresses near-certainty based on clear evidence — for example, hearing a doorbell and concluding a guest has arrived, or seeing wet ground and deciding it rained.

例句

The kitchen light is on, so Mateo must be home by now.

廚房的燈亮著，所以 Mateo 現在一定在家。

must + base verb — logical conclusion from visible evidence

You have been walking all day — your feet must hurt.

你走了一整天了——你的腳一定很痠。

同義詞
  • have to

    can express certainty: 'That has to be the right answer.'

  • be bound to

    slightly more formal; emphasises inevitability: 'She is bound to be tired after the trip.'

  • can only be

    used when only one explanation fits: 'It can only be him.'

反義詞
  • cannot / can't

    the logical negative — expresses certainty that something is NOT true

文法句型

must + base verb (present deduction)

must have + past participle (past deduction)

must be + adjective/noun

用法筆記

For past deduction, use 'must have + past participle' (e.g., 'She must have left the key on the table'). The negative of this sense is 'cannot / can't + base verb' or 'cannot / can't have + past participle' (e.g., 'He cannot be at work — his car is still in the driveway'), NOT 'must not', which expresses prohibition, not logical impossibility.

常見錯誤

❌He must not be at home — his car is there.
✅He cannot be at home
💡his car is there.' — 'must not' means prohibition; use 'cannot / can't' for logical impossibility.
❌She must be left already.
✅She must have left already.
💡For past deduction, use 'must have + past participle', not 'must be + past participle'.

must — 名詞

must — 字首