它是什么？
动词 to be 用于描述人、事物、地点、感觉、年龄、职业和情况。
现在时形式有：
- am
- is
- are
am 与 I 连用。
- I am tired.
is 与 he、she 和 it 连用。
- He is at home.
- She is a teacher.
- It is cold.
are 与 you、we 和 they 连用。
- You are ready.
- We are friends.
- They are busy.
何时使用
使用 to be 来谈论：
- 身份：I am Daniel.
- 职业：She is a nurse.
- 年龄：He is twenty years old.
- 感觉：We are happy.
- 描述：The room is small.
- 地点：They are at work.
- 国籍：She is Canadian.
- 天气和时间：It is cold. It is six o’clock.
使用否定形式来表示某事不是真的。
- I am not tired.
- He is not at home.
- They are not ready.
使用疑问句来询问身份、状况、地点、年龄或描述。
- Are you tired?
- Is she at work?
- Are they students?
结构
肯定句
使用：
主语 + am/is/are + 表语
| 主语 | 形式 | 例句 |
|---|---|---|
| I | am | I am ready. |
| he / she / it | is | She is busy. |
| you / we / they | are | They are outside. |
常见的缩略形式有：
| 完整形式 | 缩略形式 |
|---|---|
| I am | I’m |
| he is | he’s |
| she is | she’s |
| it is | it’s |
| you are | you’re |
| we are | we’re |
| they are | they’re |
否定句
使用：
主语 + am/is/are + not + 表语
| 主语 | 完整形式 | 缩略形式 |
|---|---|---|
| I | am not | I’m not |
| he / she / it | is not | isn’t |
| you / we / they | are not | aren’t |
例如：
- I’m not hungry.
- She isn’t at home.
- We aren’t late.
he’s not、she’s not、you’re not 和 they’re not 这些形式也是正确的。
疑问句
将 am、is 或 are 放在主语之前。
am/is/are + 主语 + 表语？
| 陈述句 | 疑问句 |
|---|---|
| You are tired. | Are you tired? |
| She is at work. | Is she at work? |
| They are ready. | Are they ready? |
| I am late. | Am I late? |
简短回答
在简短回答中使用 am、is 或 are。
- Are you ready? — Yes, I am.
- Is he at home? — No, he isn’t.
- Are they busy? — Yes, they are.
- Is she a doctor? — No, she isn’t.
在简短回答中通常不使用肯定缩略形式。
- 正确：Yes, I am.
- 错误：Yes, I’m.
例句
- I am a software developer.
- She is very tired today.
- They are at the bus stop.
- I’m not hungry.
- He isn’t at work.
- We aren’t ready yet.
- Are you from Canada?
- Is your brother at home?
- Are the children tired?
- Why is the door open?
例外情况
在正式疑问句中使用 am I not?。
- Am I not invited?
在日常英语中，aren’t I? 常用于否定疑问句和附加疑问句。
- Aren’t I invited?
- I’m late, aren’t I?
不要将 do、does 或 did 与 to be 连用。
- 正确：Is she tired?
- 错误：Does she be tired?
动词 to be 在简单描述中不需要单独的主要动词。
- She is happy.
- They are at home.
常见错误
-
错误： I is tired. 正确： I am tired. 解释： 使用 am 与 I 连用。
-
错误： They is at home. 正确： They are at home. 解释： 使用 are 与 they 连用。
-
错误： She not is ready. 正确： She is not ready. 解释： 将 not 放在 is 之后。
-
错误： I don’t am hungry. 正确： I am not hungry. 解释： 不要将 do 与 to be 连用。
-
错误： Does he be at work? 正确： Is he at work? 解释： 将 is 放在主语之前构成疑问句。
-
错误： Are she tired? 正确： Is she tired? 解释： 使用 is 与 she 连用。
-
错误： Is they ready? 正确： Are they ready? 解释： 使用 are 与 they 连用。
-
错误： Yes, I’m. 正确： Yes, I am. 解释： 在简短回答中通常不使用肯定缩略形式。