英语be动词是什么？动词又是什么？

be
助词 v.aux.

1.(与动词的现在分词连用,构成各种进行时态)正在...,在...
I won't be free this afternoon. I'll be seeing a friend off.
我今天下午没空,我要给朋友送行。
What were you doing from 9 to 11 this morning?
今天上午九点到十一点你在做什么?
He is working.
他在工作。
2.(与及物动词的过去分词连用,构成被动语态)被...
The problem was solved long ago.
问题早解决了。
It will be discussed tomorrow.
此事将在明天讨论。
3.【旧】(与不及物动词go,come,rise等的过去分词连用,构成完成时)已经...
The sun is set.
太阳已经下山。
4.(与动词不定式连用,表示职责、义务、意图、约定、可能性等)应该做...,必须做 ...;预定做...;会做...
The President is to visit Japan next week.
总统将于下周访问日本。
You're to do your homework before you watch TV.
你应该做了功课再看电视。

不及物动词 vi.

1.是[L]
At that time he was the chair of the department.
当时他是系主任。
I am a teacher and they are my students.
我是老师,他们是我的学生。
She is very young.
她非常年轻。
2.(表示时间、度、量、价值等)是;值;等于[L]
The watch is 100 dollars.
这表值一百元。