Can and Be Able To
时间：2019-02-06 作者：英语课 分类：2019年VOA慢速英语(一)月
Modal verbs are helping 1 verbs. We use them with main verbs to help us express ability, possibility, necessity 2 and permission. Today’s question is about a modal that is commonly confused with an expression. Here’s the question, which comes from a listener named Cafer:
Question
Hi! Would you like to explain the difference between “can” and “be able to”? Thank you. -Cafer ?zcan?
Answer
Hi, Cafer!
I can explain the differences between the two.
I just used “can” to talk about my ability to do something. We also use “be able to” for abilities, but usually only when “can” is not possible. I’ll tell you what that means in a minute.
But first, let’s explore the word “can.”
Can
“Can” is a modal verb. We use it to:
talk about present or future ability or possibility
I can play the guitar.
You can buy the tickets online.
You must use “could” for the past tense, such as in, “You could have bought the tickets online.”
We also use “can” to:
ask for or give permission?
I am finished. Can I go now?
Yes, you can.
and to ask someone to do something?
Can you bring me the magazine?
Be able to
Now, let’s explore “be able to.”
This expression is not a modal. It is the verb “to be” plus the adjective 3 “able.” The word “to” shows that an infinitive 4 verb will follow.
We use “be able to”:
when it is not possible to use “can” for abilities, such as after other modal verbs?
I won’t be able to take you to the train station. Sorry!
You should be able to finish the book in a few days.
The words “won’t”, short for “will not”, and “should” are modals. In English, we do not put two modals together. So, we cannot put “can” after them.
We also use “be able to”:
to talk about small or large past successes.?
We were able to get a great price on the television.
She was able to win the math competition last month.
But in negative form, we can use "be able to” or “could”:?
We couldn’t get a great price on the television.
She wasn’t able to win the math competition last month.
But note that the negatives "wasn’t able to" and "weren’t able to" are a little more formal than "couldn't."
And that’s Ask a Teacher.
I’m Alice Bryant.
Words in This Story
confuse – v. to make someone unable to understand something
guitar – n. a musical instrument that is held against the front of your body and that has six strings 5
infinitive – n. the basic form of a verb
negative – adj. describing a word or statement that means “no” or that expresses a denial or refusal
- The poor children regularly pony up for a second helping of my hamburger. 那些可怜的孩子们总是要求我把我的汉堡包再给他们一份。
- By doing this, they may at times be helping to restore competition. 这样一来, 他在某些时候,有助于竞争的加强。
- I look upon this as an absolute necessity.我认为这是绝对必要的。
- You must understand the necessity of education.你必须懂得教育的必要性。
- Don't apply that adjective to me.不要用那个字眼来形容我。
- The adjective loose has several senses. 形容词loose有几个义项。
- The use of the split infinitive is now generally acceptable.分裂不定式的用法现在已被广泛接受。
- Modal verbs generally take the bare infinitive.情态动词通常用不带to的不定式。