精熟 am, is, are 的肯定、否定與疑問句，搭建穩固的語法基石。
語法基石：主詞與 Be 動詞的一致性
在開始造句之前，必須先掌握 Be 動詞的黃金規則：它的形式 (am/is/are) 完全由主詞決定。這種主詞與動詞之間的配合關係，稱為「主詞動詞一致性」。
| 主詞 (Subject) | Be 動詞 (Verb) | 範例 (Example) |
|---|---|---|
| I (我) | am | I am a student. |
| He, She, It 單數名詞 (the cat) | is | He is tall. / The cat is cute. |
| You, We, They 複數名詞 (the cats) | are | You are smart. / They are students. |
Be 動詞句型變化
肯定句 (Affirmative Sentences)
肯定句是用來直接陳述事實。在口語和非正式書寫中，主詞和 Be 動詞經常會「縮寫」在一起，讓表達更流暢。
| 完整形式 | 縮寫 | 範例 |
|---|---|---|
| I am | I'm | I'm a teacher. |
| You are | You're | You're in the park. |
| He is | He's | He's busy. |
| She is | She's | She's my sister. |
| It is | It's | It's a sunny day. |
| We are | We're | We're ready. |
| They are | They're | They're from Canada. |
否定句 (Negative Sentences)
要將 Be 動詞的句子變成否定句非常簡單，只需要在 Be 動詞 (am, is, are) 的後面加上 not 即可。
| 完整形式 | 縮寫形式 | 範例 |
|---|---|---|
| is not | isn't | He isn't here. |
| are not | aren't | We aren't sad. |
| am not | (無標準縮寫) | I'm not tired. (通常縮寫主詞) |
Yes/No 疑問句與簡答
要提出可以用「Yes」或「No」來回答的問題，只需要將 Be 動詞移到主詞的前面。回答時通常使用「簡答」。
句型: Be動詞 (Am/Is/Are) + 主詞 + ...?
簡答句型: Yes, 主詞 + Be動詞. / No, 主詞 + Be動詞 + not.
範例對話:
- A: Is she your friend? (她是你的朋友嗎？)
B: Yes, she is. / No, she isn't. - A: Are they ready? (他們準備好了嗎？)
B: Yes, they are. / No, they aren't. - A: Am I late? (我遲到了嗎？)
B: Yes, you are. / No, you aren't.
語法焦點：問與答的人稱轉換
問句主詞是 I 時, 回答用 you。問句主詞是 you 時, 回答用 I 或 we。
互動測驗：Be 動詞大挑戰
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