Be動詞有三個，am，is還有are。我用am，你用are，s跟著他她它，復數全部都用are。如果遇到過去時，was來把am，is替，were來把換掉動詞are。
初中英語動詞知識點：Be動詞的定義
do和be動詞的用法區(qū)別。
Be 動詞就是(am，are，is)句子中如果沒有實意動詞(例如：write，buy)之類的動詞，就直接在主語后面加Be動詞。而如果是句子中有實意動詞，那么如果你要改為一般疑問句，就要借助DO(do也稱為助動詞)，例如：I study.
改為一般疑問句：Do you study ?
順口溜：be氏三朵花， am， is還有are，
我(I)戀am， 你(you)戀are，
is跟了他(he)她(she)它(it)，
單娶is， 復娶are。
詳細講解：
英語的be 動詞是個用法比較復雜的動詞。復雜的原因有兩點：
1、除了原形的be 之外，對于不同人稱代詞以及單數名詞和復數名詞，be 會有各種變化形式和縮寫形式。概括一下有七種形式：be，am，is，are，was，were，been，being。它們與人稱代詞和名詞單、復數的搭配關系是：
現在時 I am，you are，he/she/it/ is，we/you/they are;名詞單數、不可數名詞用is，復數用are。
縮略式 I'm，you're，he's，we're，you're，they're
否定縮略式 I'm not，isn't，aren't
過去時 I was，you were，he/she/it/ was，we/you/they were;名詞單數、不可數名詞用was，復數用were。
否定縮略式 wasn't，weren't
過去分詞 been
現在分詞 being
2、在句子中，be有兩種主要作用：一是作為系動詞(The Linking Verb)，本身可以作用謂語動詞;二是做為助動詞(The Auxiliary Verb)，與謂語動詞一起構成各種時態(tài)和被動語態(tài)等。
初中英語動詞知識點：Be動詞的用法
一、be 動詞做系動詞
1、系動詞+表語”的結構
當be 動詞做系動詞使用時，主要構成“系動詞+表語”的結構，在句子中做謂語。表語可以是名詞、形容詞、副詞、介詞短語等。例如：
The man is a science teacher.
Mary's new dresses are colourful.
Mother is in the kitchen now.
I have been there before.
They shall be here at 10:00 tommorow.
That can't be true.
You are not being very polite.
Your brother is being very annoying this evening
2、be 動詞的一般疑問句，方法是把be 移到主語前面，也可說成是移到句首。
Is the man a science teacher? Yes, he is. / No, he isn't.
Are Mary's new dresses colourful? Yes, they are. / No, they aren't.
Was mother in the kitchen then? Yes, she was. / No, she wasn't.
Were you at home the day before yesterday? Yes, I was. / No, I wasn't.
Was she late this morning? Yes, she was. / No, she wasn't.
3、be 動詞用在特殊疑問句
在特殊疑問句里，be 動詞仍然移到主語前面，但特殊疑問句是以特殊疑問詞開頭的，所以be 動詞只能說是移到主語前面，或者說是在特殊疑問詞的后面。例如：
Whose bike is broken? Xiao Ming's bike is.
Who was singing in the room? Mr. Zhang was.
Where are you from? I am from Wuhu.
What class were you in? We were in Class 2.
How old is Tom? He is ten.
4、be 動詞的否定句
be 動詞做謂語時，它的否定形式是在be 后加not，并且可以縮寫。例如：
It is not sunny today.
Tom and his friends are not in the park.
You were not nine years old when I went to the university.
He was not often late for his class when he was a student.
I wasn't here yesterday.
My parents weren't at home last Sunday.
5、be 動詞的祈使句
be 動詞的祈使句有肯定和否定兩種形式。肯定形式是以be 動詞開頭，而否定形式或強調句形，要加don't 或do。例如：
Be careful!
Be a good boy!
Don't be silly!
Don't be a fool!
Do be obedient!
Do be careful.
二、be 動詞做助動詞
助動詞be 有兩個基本用法，一是與謂語動詞一起構成各種時態(tài)，二是構成被動語態(tài)。
“be + 現在分詞組”成各種進行式時態(tài)。例如：
Tony's maid is washing his new car.
The children are playing in the field.
Samuel was eating when I came in.
We have been living here since 1959.
This time next day they will be sitting in the cinema.
三、注意事項
英語句子中，為了表達時態(tài)或被動語態(tài)的需要，常常會出現幾個助動詞連在一塊兒使用。也就是說，助動詞be會和其它助動詞一起使用。這時候，整個句子的一般疑問句和否定句，就不一定是對be 進行變化了，而是以第一個助動詞為主進行變化。即哪個助動詞在先，就以它為主進行變化。例如：
[肯定句] All the wonderful birds can be found in our Bird Park. (助動詞有兩個：can be )
[疑問句] Can all the wonderful birds be found in our Bird Park? (移第一個can)
[否定句] All the wonderful birds can not be found in our Bird Park. (在第一個can 后加not)
[肯定句] I have been there before. (兩個助動詞：have， been )
[疑問句] Have you been there before?
[否定句] I have not been there before.
[肯定句] I shall be having my supper at six tomorrow evening. (兩個助動詞：shall， be )
[疑問句] Will you be having my supper at six tomorrow evening?
[否定句] I shall not be having my supper at six tomorrow evening.
四、助動詞be，無詞義，輔助主要動詞一起在句中作謂語動詞。用法如下：
1. be+doing：構成進行時態(tài)，有現在和過去兩種進行時態(tài)。如：
The girls is reading and copying the new words now.
Young Tom was always asking questions and trying out new ideas.
2. be+going to do，表示“打算或將要做某事”，be有現在和過去兩種形式。如：
We are going to plant trees in the park.
I didn’t know if she was going to come here.
3. be+to do，表示“按計劃安排將要做某事”。如：
The new shop is not to be opened till next Monday. One night an angel came to
Mary and told her that she was to have this special boy.
五、there be
there be句式為：there be+主語部分+狀語部分，表示“某處存在某物”，be常用現在時，過去時和將來時等。如：
Oh, cool! And there are many things to see. There is even a deer park in Sanya.
There are about 80 pyramids in Egypt.
Will there be a football match in your school next week?
六、實義be
可以將be視為實義動詞，因為它具有實際的詞義，如“成為;做;發(fā)生;舉行;逗留;到達”等。如：His daughter wants to be a doctor for animals in her twenties.Kates birthday party
will be at half past six this evening.Jim has been in China for
morethan two years, but he has not yet been to Yichang.