助动词的形式与作用
[英语语法手册]助动词
1)英语常用的助动词(auxiliary verb)有shall，will，should，would，be，have，do等。助动词一般无词义，不能单独作谓语动词。助动词在句中的作用，在于帮助构成各种时态、语态、语气、否定和疑问结构等。如：
China has entered a great new era. 中国已进入了一个伟大的新时期。(帮助构成完成时态)
Some boys are playing on the grass. 一些男孩正在草地上玩。 (帮助构成进行时态)
Mother is written by Gorky. 《母亲》是高尔基写的。 (帮助构成被动语态)
We Shall have the football match if it does not rain.如果不下雨，我们就赛足球。(帮助构成将来时态和否定结构)
Do you see my point? 你明白我的意思吗?(帮助构成疑问结构)
[注]在否定结构中，not须放在助动词后面。
2)助动词加not一般都有简略式，用于口语中。如：
is not-isn't would not--wouldn't
are not--aren't [B:nt] have not--haven't
was not -- wasn't has not--hasn't
were not-- weren't [wE:nt] had not--hadn't
shall not--shan't [FB:nt] do not--don't [dEunt]
will not--won't [wEunt] does not--doesn't
should not--shouldn't did not--didn't
be