be动词的意思和用法有很多，跟不同的词搭配使用，在不同的句子中，汉语意思比较灵活。

be动词有三个，分别是is，am，are。

1. 与人称代词连用

口诀: 我用am，你用are，is连着他她它，单数用is，复数就用are。

I am = I'm I am not = I'm not

you are = you're you are not = you aren't

He is = He's He is not = He isn't

She is = She's She is not = She isn't

It is = It's It is not = It isn't

例句:

I'm Amy. 我叫艾米。

You are welcome. 不客气。

He is tall. 他个子高。

She is pretty. 她很漂亮。

It's a dog. 它是一只狗。

2. 与指示代词连用

This is 这是～ That is = That's 那是～

This is not～ That is not = That isn't～

These are 这些是～ Those are 那些是～

These aren't Those aren't

例句:

This is my family. 这是我的家庭。

That is my brother. 那是我的哥哥。

These are my shoes. 这些是我的鞋。

Those are cats. 那些是绵羊。

3. There be 句型

（肯定）There is + 可数名词单数/不可数名词

（否定）There isn't + 可数名词单数/不可数名词

（肯定）There are + 可数名词复数

（否定）There aren't + 可数名词复数

There is a book on the desk.

在桌子上有一本书。

There are some pens in the pencil box.

在文具盒里有一些钢笔。

There isn't any milk in the glass.

杯子里没有牛奶了。

4. 主系表结构

主语是单数，be动词用is

主语是复数，be动词用are

主语是不可数名词，be动词用is

The cat is in the box. 猫在盒子里。

The children are playing football.

孩子们在踢足球。