be是一個多功能動詞，在初級英語里可見四種用法：
功能一，系動詞be
be為連系動詞，中心詞義是"是"，句型為"主+系+表"結構。be的形式常用am, is, are(現在式);was, were(過去式);will/can/may/must be(助動詞/情態動詞+原形);have/has/had been(助動詞+過去分詞)等。如：
To help animals is helping people.(一般現在時)
The twins were very busy yesterday.(一般過去時)
It will be sunny tomorrow.(一般將來時)
She has been ill for over a week.(現在完成時)
功能二，助動詞be
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，有現在和過去兩種進行時態。如：
The girls is reading and copying the new words now.
Young Tom was always asking questions and trying out new ideas.
2. be+done：構成被動語態(主語是動作的承受者，done必須是及物動詞)。如：
Tea is grown in my hometown.(一般現在時的被動語態)
This building was built three years ago.(一般過去時的被動語態)
Our classroom has been cleaned and tidied already.(現在完成時的被動語態)
How could this kind of cakes be made in your home?(含情態動詞的被動語態)
That is a day never to be forgotten.(動詞不定式的被動語態)
3. 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.
4. 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.
功能三，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?
功能四，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;發生;舉行;逗留;到達"等。如：
His daughter wants to be a doctor for animals in her twenties.
Kate’s birthday party will be at half past six this evening.
Jim has been in China for more than two years, but he has not yet been to Yichang.
