主要助動詞 (Primary Auxiliaries)
主要助動詞有三個：be, do, have。它們除了可以當主要動詞，也常被用來幫助其他動詞。
be (am, is, are, was, were, being, been) v. [bi] 是；存在 (助動詞)
Used with a present participle (-ing) to form continuous tenses, or with a past participle to form the passive voice. (與現在分詞連用構成進行式；與過去分詞連用構成被動語態。)
She is reading. (她正在閱讀。 - 構成現在進行式)
The book was written by him. (這本書是被他寫的。 - 構成被動語態)
do (does, did, doing, done) v. [du] 做 (助動詞)
Used with a main verb to form negative and interrogative sentences in the simple present and simple past tenses. (與主要動詞連用，構成現在簡單式和過去簡單式的否定句和疑問句。)
I do not (don't) like coffee. (我不喜歡咖啡。 - 否定)
Does she speak English? (她說英語嗎？ - 疑問)
Did you go out last night? (你昨晚出去了嗎？ - 疑問)
have (has, had, having) v. [hæv] 有；擁有 (助動詞)
Used with a past participle to form perfect tenses. (與過去分詞連用構成完成式。)
I have finished my work. (我已經完成我的工作了。 - 現在完成式)
She had already left when I arrived. (我到達時她已經離開了。 - 過去完成式)
情態助動詞 (Modal Auxiliaries / Modal Verbs)
情態動詞用來表達說話者的語氣、態度或看法，例如能力、許可、可能性、義務、建議等。它們後面**必須**接**動詞原形**！
can v. [kæn] 能夠；可以 (表能力、許可)
To be able to do something; to be permitted to do something. (能夠做某事；被允許做某事。)
I can swim. (我會游泳。)
Can I use your phone? (我可以用你的電話嗎？)
could v. [kʊd] 能夠；可以 (can 的過去式)；(委婉)可以；可能
Past tense of can; used to express possibility or make polite requests. (can 的過去式；用來表達可能性或提出禮貌請求。)
I could run fast when I was young. (我年輕時能跑很快。)
Could you help me, please? (可以請你幫我嗎？)
It could rain later. (等一下可能會下雨。)
may v. [me] 可以 (表許可)；可能 (表可能性)
Used to express permission or possibility. (用來表達允許或可能性。)
May I ask a question? (我可以問個問題嗎？ - 較 can 正式)
He may be late for the meeting. (他開會可能會遲到。)
might v. [maɪt] 可能 (可能性較 may 低)
Used to express possibility (less probable than may). (用來表達可能性，可能性比 may 低。)
It might snow tomorrow, but it's unlikely. (明天可能會下雪，但不太可能。)
must v. [mʌst] 必須；一定
Used to express necessity or obligation; used to express strong belief. (用來表達必要性或義務；用來表達強烈的相信。)
You must follow the rules. (你必須遵守規則。)
He hasn't eaten all day. He must be hungry. (他整天沒吃東西。他一定餓了。)
shall v. [ʃæl] 將要 (用於第一人稱 I/we，表建議或徵求意見，現較少用)；應該
Used with I/we to express the future tense (less common now); used in questions to make offers or suggestions. (與 I/we 連用表示未來式（現較少用）；用於問句表示提議或建議。)
Shall we dance? (我們跳舞好嗎？)
What shall I do now? (我現在該怎麼辦？)
注意：在現代英語中，表未來常用 will 代替。
should v. [ʃʊd] 應該 (表建議、義務或推測)
Used to indicate obligation, duty, or correctness, typically when criticizing someone's actions; used to indicate what is probable. (用來指示義務、責任或正確性，尤指批評某人行為時；用來指示可能的情況。)
You should apologize to her. (你應該向她道歉。)
He should be here by now. (他現在應該到這裡了。)
will v. [wɪl] 將要；意願 (過去式: would)
Used to express future tense; used to express willingness or determination. (用來表達未來式；用來表達意願或決心。)
It will rain tomorrow. (明天將會下雨。)
I will help you if you want. (如果你想要，我會幫你。)
would v. [wʊd] 將要 (will 的過去式)；(委婉)願意；(過去)習慣於
Past tense of will; used to express polite requests or hypothetical situations; used to express habitual past actions. (will 的過去式；用來表達禮貌請求或假設情況；用來表達過去的習慣性動作。)
He said he would come. (他說他會來。 - will 的過去式)
Would you like some tea? (你想要一些茶嗎？ - 委婉請求)
When I was a child, I would often play here. (我小時候，常常會在這裡玩。 - 過去習慣)
need v. [nid] 需要 (也可當情態動詞，表「需要；必須」，多用於否定 needn't 或疑問)
To require something because it is essential. / (As modal) Must have or do something. (因為必需而需要某物。/ (作為情態動詞) 必須擁有或做某事。)
You need to finish this today. (你需要今天完成這個。 - 一般動詞)
You needn't worry about it. (你不必擔心。 - 情態動詞，= don't need to)
Need I say more? (我還需要多說嗎？ - 情態動詞，疑問)
詞彙小叮嚀：
- **助動詞 (be, do, have)** 主要幫助形成時態、否定和疑問。
- **情態動詞 (can, could, may, might, must, shall, should, will, would...)** 表達語氣，後面**永遠接動詞原形**！
- 情態動詞本身沒有人稱和數的變化 (例如 He can swim. 不是 He cans swim.)。
- 否定直接在情態動詞後加 not (can't, couldn't, won't, shouldn't...)。
- 疑問句將情態動詞移到主詞前。
- 掌握這些動詞小幫手，你的句子就能表達更豐富的意思和時態了！