Do you know the difference between ‘can’ and ‘be able to’? Well, to start with, ‘can’ is a modal verb, while ‘be able to’ is not. But what about usage? Let’s have a look:
I can play the guitar
I am able to play the guitar.
Ability
In these examples, they can be used in exactly the same way. And that is because, to all intents and purposes, ‘can’ and ‘be able to’ are both used, primarily, to express ability. Of course, both of these examples above are in the present tense, so matters get a little more complicated when we change that tense.
In the past
The past form of ‘can’ is ‘could’. ‘Be able to’, because it is using the verb ‘be’, can be easily adapted into any tense. So, therefore,
I could play the guitar when I was younger.
I was able to play the guitar when I was younger.
So, again, when talking about ability in the past, ‘could’ and ‘be able to’ operate in the same way. But only if we are talking about general abilities. In the case of a single action, ‘could’ is not possible.
Yesterday, I was able to meet lots of interesting people at the meeting.
Yesterday, I could meet lots of interesting people at the meeting.
However, if that single event involves a stative verb, then it would be possible.
Yesterday, I was able to see the screen really clearly from where I was sitting.
Yesterday, I could see the screen really clearly from where I was sitting
In the future
There is no future form of ‘can’ (‘will can’ is an absolute impossibility). Therefore, if you want to express a future ability, ‘be able to’ is your best friend here
In the future, I will be able to play the guitar.
You could also make a more complicated sentence, such as:
In the future, I will have the ability to play the guitar.
However, when talking about future plans and arrangements, you can use ‘can’ (as well as ‘be able to’):
I can attend the appointment next Monday.
I am able to attend the appointment next Monday.
These two sentences have exactly the same meaning.
So, in summary, when talking about ability, ‘be able to’ is a much more flexible option.
Semantics
We may also choose to use these two forms a little differently to emphasize the difference between a permanent ability, and the ability to do something at the moment. Here is another example:
I am able to play the guitar, but I can’t play the guitar at your wedding because I am unavailable that day.
In theory, you could invert those two terms to produce the same meaning in context, but the preference would be to use ‘be able to’ in order to talk about a permanent skill, rather than the ability to do something on any given day.
Talking about permission
‘Can’ and ‘be able to’ are not only about ability but are connected to permission too. Look at these examples:
My teacher says I can use a dictionary in the classroom.
My teacher says I am able to use a dictionary in the classroom.
In these instances, ‘can’ and ‘be able to’ are the same.
However, when it comes to talking about permission, even in the present tense, you cannot always use both options. Here’s another example:
My teacher says I can bring a dictionary to the exam tomorrow.
My teacher says I am able to bring a dictionary to the exam tomorrow.
In this case, ‘be able to’ would not be used to express permission in a specific, once-off event.
My teacher says I am allowed to bring a dictionary to the exam tomorrow.
This would be correct and has the same meaning as ‘can’ in the sentence above.
However, in one last twist, you could (or you are able) to use ‘be able to’ in this situation, if you are talking about your ability to do something:
My teacher says I can bring a dictionary to the exam tomorrow. = permission
My teacher says I am able to bring a dictionary to the exam tomorrow. = ability
Although the second sentence doesn’t really make any sense, it focuses more on the ability to do something, rather than the giving of permission.
In conclusion
‘Be able to’ definitely offers more flexibility than ‘can’ in terms of conjugating to verb tenses. However, the meanings are not always the same, and there are certain circumstances where either ‘can’ or ‘be able to’ are not logical.
Always consider this question: am I talking about ability or permission? Once you have ascertained this, and then you have decided upon the correct verb tense, making the right decision in terms of ‘can’ and ‘be able to’ should be achievable.
