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Modal verbs are helping verbs.
情态动词是助动词。
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。
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。
Here's the question, which comes from a listener named Cafer:
今天的问题来自于Cafer。
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。
I just used "can" to talk about my ability to do something.
我用“can”表达我能做某事。
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。
I'll tell you what that means in a minute.
稍后我会告诉你是什么意思。
But first, let's explore the word "can."
首先我们来看一下“can”这个单词。
"Can" is a modal verb.
“can”是一个情态动词。
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。
I can play the guitar.
我能弹吉他。
You can buy the tickets online.
你可以在网上购票。
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。”
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。
I am finished. Can I go now? Yes, you can.
我完事了，现在可以走吗？你可以走。
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”。
This expression is not a modal.
这个表达不是情态动词。
It is the verb "to be" plus the adjective "able."
是动词“to be”加上形容词“able”。
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。
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。
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。
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。
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。
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。
So, we cannot put "can" after them.
所以我们不能把“can”放在它们后面。
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。
We were able to get a great price on the television.
我们的电视买的很划算。
She was able to win the math competition last month.
她上个月在数学竞赛中获胜了。
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。
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。
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。
And that's Ask a Teacher.
以上就是今日名师答疑的全部内容。
I'm Alice Bryant.
我是艾莉丝·布莱恩特。
