Can vs be able to, the difference?
출처 https://langeek.co/en/grammar/course/631/can-vs-able-to
"Can" and "be able to" are both used to show ability 둘 다 능력 의미로 쓰인다
but the main difference between them is in their parts of speech. 차이는 품사의 역할이다
"Can" is a modal verb and "be able to" is a phrasal verb. 하나는 조동사 다른 하나는 동사구 역할
즉 조동사는 동사의 도우미 역할이므로 동사 없이 못 쓰이나 동사구는 그 자체로 동사 역할을 함
* Can 조동사
"Can" is one of the most commonly known modal verbs (also known as modals or modal auxiliary verbs) used
to talk about possibilities, ask for or give permissions, request something, etc.
We use can to refer to the present and the future.
can은 능력, 가능성, 허락, 요청 등의 의미를 동사에 추가하는데 쓰임
Have a look:
Example
I can talk about my favorite movie all day.
I can stay overtime tomorrow.
* Be Able to 동사구
"Be able to" is a verb phrase.
We use "be able to" to talk about abilities. 능력을 얘기할 때 쓰이며 과거와 현재 시제로 활용된다
The presence of the auxiliary verb "be" allows us to use the phrase in both present and past tense.
Be able to+동사=동사구가 되므로 Be able to 부분을 조동사처럼 이해하면 쉽다
Example
He was able to jump really high.
He is able to jump really high.
(미래는 He will be able to jump really high.)
* Similarities 유사점
Talking about Abilities 능력 의미로 쓰일 때는 같다
We use "can" and "be able to" to talk about abilities, knowledge, or talent.
We use "can" to talk about the present and the future.
"Be able to" is used in all tenses to show ability.
For example:
I can teach English.
I was able to teach English.
I am able to teach English.
I will be able to teach English.
(다만 can은 특성적인 능력, able to는 특정 상황에서의 한시적인 능력을 의미한다)
* Negation 부정문
When we want to make negative sentences, we use "cannot" and "not able to" or "unable to." For instance:
Example
I cannot teach English.
I am not able to teach English.
I am unable to teach English.
* Differences 차이점
1. Parts of Speech 품사
"Can" is a modal verb that is used to give additional information about the function of the main verb.
Have a look:
Example
I can ride a bicycle.
They can whistle.
2. "Be able to" is a phrasal verb.
A phrasal verb is a phrase that functions as a verb. Take a look at the following example:
Example
I am able to ride a bicycle.
They are able to whistle.
* With Modals 조동사와 함께 쓰기
3. "Can" is a modal verb and we cannot use two modals in one sentence at once.
In this case, we use "to be verb" since we can use it with other modals. Have a look:
조동사는 접속사 없이 두 개를 같이 못 쓴다
Example
I should can work with a broken keyboard.
(I should AND can work with a broken keyboard.은 문법상 가능함)
I should be able to work with a broken keyboard.
4. With Tenses 시제 문제
We use "can" and "be able to" with tenses:
1. Past Tense 과거 시제
We cannot use "can" itself to talk about the past.
Instead, we use "could.
"With "be able to," we use the past tense of the auxiliary verb "be": was/were.
Take a look at the following example:
Example
I can run fast when I was younger. → I could run fast when I was younger.
(could는 잘 못 쓰면 가정법 조동사로 오해될 소지가 있다)
I was able to run fast when I was younger.
2. Present Tense 현재 시제
We can use both "can" and "be able to" to talk about present abilities.
"Can" is more common than "be able to." Here are some examples: 격식과 비격식 차이가 있다
Example
Harry can play multiple sports.
Harry is able to play multiple sports.
3. Future Tense 미래시제
We use "be able to" to talk about having an ability in the future.
This ability is not available right now and will only be achieved in the future.
For example:
Example
I will be able to see again after the operation.
I can see again after the operation.
Here, we are talking about the present rather than the future.
* 예문에서 보았듯 can은 특성적/보유 중인 능력이라 현재나 미래 둘 다 쓰이지만
be able to를 미래 시제로 쓰면 현재는 못 한다는 암시가 나오므로 한시적인 능력이다
We use both "can" and "be able to" to talk about future decisions and arrangements.
Have a look:
Example
I can give you a hand tomorrow. (can의 미래는 미래 의미의 시간부사를 써서 표시한다)
I will be able to give you a hand tomorrow. (be able to는 조동사 will을 사용한다)
* Questions 의문문 만들기
Both "can" and "be able to" are used to make questions.
"Can" is simply inverted to create questions. Watch:
Example
I can swim. → Can I swim?
You can give an example. → Can you give an example?
To make a question with "be able to," we invert the "be" and do not change the position of "able to." Consider the following examples:
Example
He is able to jump high enough. → Is he able to jump high enough?
They are able to make it to the meeting. → Are they able to make it to the meeting?