一、 基本用法 1. 表示能力（如体力和脑力方面），意为“能；会”等。例如： Can you speak English? 你会讲英语吗？ Can you play the piano? 你会弹钢琴吗？

2. 表示请求或允许，多用在口语中，意为“可以；能”等。用于疑问句中用来提出要求，用于否定句表示不允许。例如： Can I help you? 我能帮助你吗？You can’t play basketball. 你不能玩篮球。 Can you...？“请你……好吗？”表示说话人的请求；Can I...？“我可以……吗？”用来征求对方是否允许自己做某事。如在句末加上 please一词就显得更有礼貌了。例如： Can you help me, please? 请你帮助我好吗？

3. 表示可能。例如： He can be at home now. 他现在可能在家。 The moon can’t always be full.月亮不可能常圆。

4. 表示怀疑。在表达此意时，只能用于一般疑问句中，带有感情色彩。例如： Can it be true? 那会是真的吗？

二、 句式变化如下： 1. 在变否定句时，直接在can后加上“not”,可缩写成can’t或cannot, 但不能写成cann’t。例如： He can swim. → He can’t swim. Emma can see the pen on the desk.→ Emma cannot see the pen on the desk.

2. 在变一般疑问句时，直接移到主语前（原主语的首字母改成小写，第一人称应变为第二人称）即可。例如： I can see an orange on the table. → Can you see an orange on the table? 其回答可用Yes, OK或Certainly等作肯定回答；用No或Sorry等作否定回答。例如： —Can you look after my books, please? 你能照看一下我的书吗？ —OK. 可以。 用Certainly回答。此时语气更为肯定。例如： —Can I see your guitar? 我能看看你的吉它吗？ —Certainly. 当然可以。 [特别提醒] can与may都可以表示“许可”。在征求对方意见时用may较多。例如：May I go now? 现在我可以走吗？在询问客观上是否可以时，can则当仁不让。例如：Can we take the books out? 我们能把这些书拿出去吗？在两者都可以用时，may显得客气一些。例如：May I take this seat? 比Can I take this seat? 稍婉转一点。在陈述句中用我较多。例如：You can sit here. 你可以坐在这里。 can还可以表示能力，而may则无此用法。

 

第二篇：as的用法小结

as的用法小结

as可以作连词、介词及关系代词。现将其用法小结如下:

一、 as作连词的用法:

1. 作"当……的时候",引导时间状语从句。注意与when、 while的用法区别。 ① when作"当……的时候"解,可以指较短的(一点)时间,也可指一段时间。如: When he was at college, he could speak several foreign languages. When the clock struck twelve, all the lights in the street went out.

② while常表示一段较长的时间或一个过程,强调主句谓语动词与从句谓语动词同时发生。如:

Work while you work. Play while you play.

③ 但属下列情形时,只用as, 而不用when或while。

A) 用于表示同一个人的两种动作交替进行,指"一边……,一边……"。如: The girl dances as she sings on the stage.

He looked behind from time to time as he went forward.

B)表示两个同步发展的动作或行为,译为"随着……"。如: As time went on / by, she became more and more worried.

As children get older, they become more and more interested in the things around them.

C)表示两个短促行为或事件几乎同时发生。如:

I thought of it just as you opened your mouth.

Just as the flying worm hit her face, she gave a loud cry.

D) 后接名词表示某一年龄段时,用as。如:

As a young man, he was active in sports.

2. as=since, 作"既然"、"由于"解,引导原因状语从句,常用来表示已为人们所知或显而易见的原因或理由。如:

As / Since you're not feeling well, you may stay at home.

As he wasn't ready in time, we went without him.

3. as=in the way that, 作"像"、"按照……的方式"解,引导方式状语从句。如:

He speaks English as Americans do.

Remember, you must do everything as I do.

4. 用于as...as...或not so/ as...as...中,前一个as是副词,后一个as是连词,引导比较状语从句。如:

They helped the old man as often as possible.

I don't speak English so/ as well as he does.

5. 作"虽然"、"尽管"解,引导让步状语从句。常用倒装语序,即adj. /adv. / n.+ as +主语+谓语+主句。如:

Tired as they were, they walked on.

Child as he is, he knows a lot. (child前不用冠词)

二、 as作关系代词,引导定语从句,作"正如"、"这一点"解。如:

He is very careful, as his work shows.

As is well-known, Taiwan belongs to China.

as的这种用法,请看20xx年的高考题:

is known to everybody, the moon travels round the earth once every month.

A. It B. As C. That D. What

字母下划横线的为正确答案)

另外,当先行词被the same, such等词修饰时,常用as来引导定语从句。如: Such a clever boy as he can learn anything quickly.

I was reading the same book as he bought yesterday.

三、 as作介词的用法:

as引导的介词短语大多用作状语,as译为"作为";少数情况可引起宾语补足语。如: As a League member, I'll take the lead in everything. (状语)

She works as a doctor. (状语)

They have me as one of their own children.(引起宾语补足语)