功能一，系動詞be
be為連繫動詞，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)
