Modal verbs are helping verbs.

情态动词是助动词i2Io(N;Fo64pULr3wG。

We use them with main verbs to help us express ability, possibility, necessity and permission.

我们把它们和动词连用来表达能力、可能性、必要性和许可OcHAck7chmz。

Today's question is about a modal that is commonly confused with an expression.

今天的问题是关于一个经常和某个表达混淆的情态动词EAI#ob~%z^。

Here's the question, which comes from a listener named Cafer:

今天的问题来自于CaferYGz6I^MQzYe[]z|5QiD。

Hi! Would you like to explain the difference between "can" and "be able to"? Thank you.

你好，可以解释一下“can”和“be able to”之间的区别吗？谢谢你！

Hi, Cafer! I can explain the differences between the two.

Cafer你好，我可以解释这两者的区别X-eGjpn5Z9_DPrJed。

I just used "can" to talk about my ability to do something.

我用“can”表达我能做某事^N[.D@yA&5T。

We also use "be able to" for abilities, but usually only when "can" is not possible.

我们也会用“be able to”表达某种能力，但通常是不能用“can”的时候Vxl)+EfhI=qBz。

I'll tell you what that means in a minute.

稍后我会告诉你是什么意思@,0|a-K2-4%tEQye;0Li。

But first, let's explore the word "can."

首先我们来看一下“can”这个单词FXeWl03XI;GH8CR33T|7。

"Can" is a modal verb.

“can”是一个情态动词pLaXZ8*qq&^41Ip。

We use it to: talk about present or future ability or possibility.

我们用它来表达：现在或将来的能力或可能性K3SIIfQ1*S4。

I can play the guitar.

我能弹吉他Pa1=VbTAiG!IsNL。

You can buy the tickets online.

你可以在网上购票b[DV+ckBr[CfJ。

You must use "could" for the past tense, such as in, "You could have bought the tickets online."

你必须用"could"来表示过去时，例如，“You could have bought the tickets online.你本来可以在网上购票的WeQWar*#@7qJPTc。”

We also use "can" to: ask for or give permission.

我们也可以用“can”表达：请求或给予许可3o9G.2SkC1a=。

I am finished. Can I go now? Yes, you can.

我完事了，现在可以走吗？你可以走TB_(8P,yD@hK。

And to ask someone to do something, Can you bring me the magazine?

或者请求某人做某事，你可以把杂志给我吗？

Now, let's explore "be able to."

现在我们来看一下“be able to”!f@+w^iFshG。

This expression is not a modal.

这个表达不是情态动词B.2M=hmwaa。

It is the verb "to be" plus the adjective "able."

是动词“to be”加上形容词“able”Z0_i_0@2[,%%vQ3。

The word "to" shows that an infinitive verb will follow.

单词“to”意味着后面会跟一个不定式动词,kx.Wx2psjLYtWi0^as。

We use "be able to": when it is not possible to use "can" for abilities, such as after other modal verbs.

我们用“be able to”：当表达能力时不能用“can”，比如在其他情态动词后面kbZb0K|Eg,vfj#e|gg。

I won't be able to take you to the train station. Sorry!

我不能送你去火车站，对不起Iz*n#JF_vQk0。

You should be able to finish the book in a few days.

你应该能在几天内读完这本书v)2Fz,1P|w%gf.dvgy-。

The words "won't", short for "will not", and "should" are modals.

单词“won't”（will not的缩写）和“should”都是情态动词miz^XsgtNqk.fmEO。

In English, we do not put two modals together.

英语中，我们不会把两个情态动词放一起连用Fkh]5x75LCk.。

So, we cannot put "can" after them.

所以我们不能把“can”放在它们后面[lOq8sSoWmO|l#。

We also use "be able to": to talk about small or large past successes.

我们也可以这样用“be able to”：谈论过去或大或小的成功ZxDlRUcW9i!T。

We were able to get a great price on the television.

我们的电视买的很划算3T8+=Vj34_qZe=WAY。

She was able to win the math competition last month.

她上个月在数学竞赛中获胜了gbyB#0NGi^n]GqLNjHoD。

But in negative form, we can use "be able to" or "could": We couldn't get a great price on the television.

但是在否定形式中，我们可以用"be able to"或者"could"，比如我们的电视买贵了sv]9K&%1K~gWfSFo。

She wasn't able to win the math competition last month.

她没能在上个月的数学竞赛中获胜3G7qyMQ1f)HE。

But note that the negatives "wasn't able to" and "weren't able to" are a little more formal than "couldn't."

但是要注意否定句中“wasn't able to”和“weren't able to”比“couldn't”更正式8*Z,=p%~quGH8。

And that's Ask a Teacher.

以上就是今日名师答疑的全部内容fN1APGH==aL=qBC%%。

I'm Alice Bryant.

我是艾莉丝·布莱恩特SJIN)tufY[X^M_yM。