“Be”除了原形的“be”之外，还有另外七种形式：am, is, are, been, being, was, were.

　　在句子中，“be”可以是主动词（The Principal Verb）或助动词（The Auxiliary Verb）.

　　当主动词时，“be”在性质上属于接系动词（The Linking Verb）, 后面要有名词、形容词、地方副词或短语作补足语（The Complement）。例如：　
　　1. The man is a science teacher.
　　2. Mary's new dresses are colourful.
　　3. I have been there before.
　　4. Mother is in the kitchen now.

　　这四个都是陈述句，可以变成疑问句，方法简单，把主语和“be”或助动词对换位置即可：　
　　5. Is the man a science teacher?
　　6. Are Mary's new dresses colourful?
　　7. Have I been there before?
　　8. Is mother in the kitchen now?

　　当“be”要在祈使句中出现时，它必须借重助动词“do”或“don't”之助，如：　
　　9. Don't be silly!
　　10. Do be obedient!
　　11. Don't be a fool!

　　“Be”有两种缩写法，如下：
　　12. He's not……/He isn't……
　　13. You're not……/You aren't……

　　但“am + not”的缩写法只有一个：

　　14. I'm not.

　　有人用“ain't”, 但这并不是标准英语。

　　谈过了“be”作主动词的功能，现在看看“be”作助动词时，有些什么用法：

　　1.“Be + 现在分词”以组成进行式时态（Continuous Tenses），如：
　　15. Tony's maid is washing his new car.
　　16. The children are playing in the field.
　　17. Samuel was eating when I came in.
　　18. We have been living here since 1959.

　　2.“Be + 过去分词”以组成被动语态（The Passive Voice）,如：
　　19. Her money in the drawer was stolen.
　　20. A number of good jobs are taken up byforeigners.
　　21. David studied in Taiwan but has been trained as a language lecturer in America.
　　22. Can all the wonderful birds be found in our Bird Park?
　　23. The disobedient boy was told to stand out- side the classroom.
　　24. Steps are being taken to reduce traffic con- gestion during peak hours.
　　25. Dishonest students will be immediately dealt with.

　　从上面例子看，“be”这动词外貌平凡，但内涵丰厚。如果没有“be”，补足语的桥梁断了。如果没有“be”,何来进行式时态和被动语态？缺了这几样重要的句式，英语还像英语吗？