“To Be” 的使用和例句
不规则动词to be是所有英语动词中最复杂的，而且恰好也是使用最多的。To be动词有am, are, is, was, 和 were，以及不带to的动词不定式be，现在分词being和过去分词been。
在本文中，我们将解释所有你需要知道的关于动词be的语法知识。我们将分享所有的表格以及何时使用它们，并为每种类型的用法提供示例。
什么是 to be 动词?
动词to be表示存在(I am here)、发生(The meeting is Tuesday)或具有某事的特征(She was a quiet child)。它是英语中最常见的动词，部分原因是它在语法中有额外的用途:to be动词可以是帮助创造其他时态的助动词，也可以是帮助描述句子主语的连系动词。
作为不规则动词，to be有其独特的形式。当动词be用于不同的主语或时态时，它可以变成am, are, is, was或were。它在某些动词时态中也有不同的写法:to be的现在分词是being。过去分词是been，不定式形式是be。
to be 动词的形式
一般现在和过去时
动词to be最常用于一般现在时和一般过去时。这些时态都使用自己的特殊单词to be，这取决于主语的人称和数量。
一般现在时
单数
复数
第一人称
(I) am
(we) are
第二人称
(you) are
(you) are
第三人称
(he/she/it) is
(they) are
Simple past tense
Singular
Plural
First person
(I) was
(we) were
Second person
(you) were
(you) were
Third person
(he/she/it) was
(they) were
to be的一般现在时和一般过去时也可用作助动词，构成现在进行时和过去进行时，表示一个正在进行或持续的动作。
和其他时态一样，在进行时态中，to be动词的变化仍然与主语相匹配。句子的主要动词总是在to be和is之后，无论主语是什么，都是现在分词形式(-ing形式)。
We are driving home right now.
We were driving for hours yesterday.
一般将来和情态形式
将来时态不像过去时态和现在时态一样。一般将来时使用情态动词will，所有情态动词都使用主动词不带动词不定式的形式，不管主语是什么。to be的不带动词不定式就是be，没有to。to be的一般将来时是这样的:
I will be in Medellin tomorrow.
I will be flying to Medellin tomorrow.
所有情态动词都可以用不带to的动词不定式be，例如can, should, might或must。只要在情态动词后加上be，如果句子是否定的，就在否定词后加上be。
You can be anything if you try.
He must be exhausted after that.
They should not be here.
现在分词
如果你想在进行时态中使用to be作为主动词呢?在这种情况下，你会使用两次to be:第一次作为助动词，第二次作为现在分词。
Don’t listen to me: I am being paranoid.
这适用于现在进行时和过去进行时，但我们通常避免在将来进行时中使用to be作为主要动词——一般将来时在这种情况下也可以使用。
[INCORRECT] I will be being hungry tomorrow.
[CORRECT] I will be hungry tomorrow.
过去分词
完成时态使用助动词have的共轭形式，后面是主动词的过去分词。
To be的过去分词是been，当to be是完成时的主要动词时使用。现在完成时使用have或has，而过去完成时使用had:
I have been tired since my first day of school.
It had been a bad day even before it started raining.
To be 的语法规则
1 主谓一致
所有的动词都必须与主语一致，这叫做主谓一致。这意味着动词的人称和数必须与主语的人称和数一致。因此，如果主语是第一人称和单数(I)，动词必须是第一人称和单数(am)。
[INCORRECT] Felipe am class president.
[INCORRECT] Felipe are class president.
[CORRECT] Felipe is class president.
大多数规则动词只在第三人称单数主语的现在时发生变化，但是be要复杂得多，因为它比其他动词有更多的形式。
主谓一致的一个特别困难的地方是什么时候使用there is和there are，我们在这里详细介绍。总而言之，当动词To be跟在后面时，动词To be跟在后面的名词的数相匹配，而不是主语的数。
[INCORRECT] There is the ducks.
[CORRECT] There are the ducks.
2 否定
虽然写否定动词会让人困惑，但写将来动词就相当简单了。在现在时和过去时中，将否定词紧接在to be之后。
You are not my enemy.
She was never on time.
对于将来时态，把否定词放在will之后，在不定式be之前。
We will not be attending.
别忘了你可以用缩略语来代替动词。这些在口语中尤其常见。
This isn’t my cup of tea.
It won’t be long now.
3 问句
动词to be在疑问句(疑问句)中也有自己的规则。其他动词用助动词do来表示是非问句，而to be则不用。然而，像其他动词一样，在是非疑问句中，to be 仍出现在主语之前，即使它用作助动词。
Is that allowed?
Were you listening?
Are they going now?
例句
To be: 现在时态
She is a natural-born leader.
I am freezing in this outfit.
To be: 过去时态
We were in danger without even knowing it.
It was the best night of the trip.
To be: 现在完成时态
You have been quiet tonight.
Umar has been our team captain for two years.
To be: 过去完成时
She had been a waitress for years before they promoted her to manager.
I had forgotten the answer when I was taking the test.
To be: 现在进行时
He is studying, so don’t bother him.
You are being awfully suspicious.
To be: 过去进行时
We were watching TV when the earthquake started.
She was being as polite as possible.
To be: 将来时态
You will be sore after exercising with me!
Their plane will be landing shortly.
To be: 情态动词
I might be wrong.
If you lived here, you would be home right now.
用be的疑问句
Is this the right room?
Was that red light always flashing?
用 be动词的否定句
We are not making enough progress.
She had never been dumped before.
用 to be 动词的祈使句
Be a friend and pay for dinner.
Don’t be a stranger!