be动词，意思和用法很多，一般的意思是:是，be动词还有成为的意思。根据句子中不同的人称、数和时间，型态，应该选择相应的be动词。下面小编告诉你三年级英语be动词用法，大家一起来看看吧!
三年级英语be动词用法:
(一)There be句型
be可以与there一起构成there be句型，用来表示存在。考虑到There be句型较为重要，内容较多，在此不做赘述，后面再找时间跟大家单独分享。今天就先给几个常见的例句。
There is a white ruler on the desk.
There were a great many people in the car race last year.
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(二)祈使句中的be
这种情况下，句子一般以Be开头或是Don't be开头，表示命令或建议等。如:
Bepatient! (耐心点!)
Don't be so hard on me! (不要对我们这么严厉!)
(三)虚拟语气中的be
be有时可以放在句首，引起虚拟语气。如:
Be he rich or poor, she will marry him.
Be it true or not, she will see it herself.
此时的be引导的句子其实相当于一个让步状语从句。以上两句话就相当于:
Whether he be rich or poor, she will marry him. (无论他是否有钱，她都会嫁给她。)
Whether it be true or not, she will see it herself. (无论这是否是真的，她都会亲自去见证。)
There be句式的特殊用法:
▲ 英语中的 There，除了表示地点“在那里”外，还有一个非常重要的用法，就是:充当引导词的角色，同时，引起句子结构上的倒装。具体表现在:
1. There be 存在句:——最原始最典型的倒装
谈到倒装句，人们都不陌生，认为它是一个很重要的句式。其实，在一个人刚刚开始学英语的时候，就已经学到了真正意义上的倒装句:There be 句型。
There is a book on the desk. 去掉引导词 There，原来的倒装句则变成:A book is on the desk.
What is there on the desk? 实际等于说:What is on the desk?
There be是倒装句，表存在，不必细说。
2. There + 不及物动词 + 主语:——最常见的倒装
There lived an man in the forest long ago. 很久以前，森林中住着一位老人。
There stands a temple on the top of the mountain. 山顶上有一座庙。
There goes the bell. Let’s have our class. 铃声响了，我们上课吧。
最后一句 There goes the bell. There 除了引起句子结构的倒装外，还提醒听者注意。
3. “There + be + 过去分词 + 主语” 和“There + be + 过去分词 + 主语”——最特殊的倒装
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▲“There + be + 过去分词 + 主语”，其实是被动语态的变式，去掉引导词 There，还原本来面目。现在，我直接使用网友的句子为例:
There are now published millions of books very year in China .
等于:Millions of books are now published very year in China.
On the following day, there was held a splendid banquet.
等于:On the following day, a splendid banquet was held.
There was shown at the exhibition an electronic computer made in Shanghai .
等于:An electronic computer made in Shanghai was shown at the exhibition.
▲“There + be + 现在分词 + 主语”，其实是不及物动词进行时态的变式，去掉引导词There，还原本来面目。现在，我直接使用网友的句子为例:
There were running in the garden a group of children aged from seven to twelve.
等于:A group of children aged from seven to twelve were running in the garden.
【我的观点】任何事物的出现都是有原因的，语言现象亦然。我认为，there 的上述用法，体现了语言的3个方面。概括起来，不外乎以下几个原因:
1. 语用方面:There 置于句首，具有提示、提醒作用。如:There goes the bell. Let’s have our class.
2. 修辞方面:There 置于句首，旨在使句子匀称。如:There was shown at the exhibition an electronic computer made in Shanghai.
若说:An electronic computer made in Shanghai was shown at the exhibition. 会显得头重脚轻。
3. 语法方面:There 置于句首，改变句子的正常结构。去掉引导词 There 之后，变成正常语序，以上三种情况的例句，分别为:
(1) There is a book on the desk. → A book is on the desk.
(2) There lived an old man in the forest long ago. → An old man lived in the forest long ago.
(3) There are now published millions of books very year in China . → Millions of books are now published very year in China.
【说明】There置于句首，如果没有实际词汇意义，往往引起句子结构的倒装。如果有实际词汇意义(“在那里”)，则不然。试比较:
There stands a temple on the top of the mountain. (There 没有实际意义)
There I saw my old friend Tom. (There表示“在那里”)
there be句式中的there什么时候可省略:
——关于how many…are there…句式中省略there 的例句:
How many letters are in your name? 你的名字有多少个字母?——摘自《美国传统英汉双解学习词典》
How many tracks are on the CD?这张激光唱片上有多少首乐曲?——摘自《牛津英语搭配词典》
How many stones are in your diamond ring? 你的钻戒上有几颗钻石?——摘自《当代美国英语学习词典》
——关于What is there…句式中保留 there 的例句:
What is there to laugh at? 有什么值得笑的? ——摘自《张道真英语语法》
What is there in the way of tools? 有什么工具吗?——摘自《麦克米伦高阶美语词典》
there’s 后可接复数名词吗:
一、通常情况
在通常情况下，若there be只有一个主语，谓语的数则取决于该主语的数;若有几个主语并列，则通常是与靠近的主语保持一致。如:
There is a book on the desk. 书桌上有一本书。
There were a lot of people waiting. 有许多人在等着。
There is a girl and two boys in the room. 房里有一个女孩和两个男孩。
但有时也可以与和两(几)个主语保持一致。如:
There were one or two chaps there. 那儿有一两个人。
In addition to her, there were Mr. and Mrs Dalby. 除了她还有戴尔比夫妇。
二、特殊情况
但是，在非正式场合，there’s 往往可以用来代替复数形式there are 用于复数名词前。如:
There’s lots of cars on the road these days. 如今路上有许多汽车。(摘自《朗文英语语法》)
There’s a man and a dog in our garden. 我们花园里有一个人和一只狗。(摘自《朗文英语语法》)
