Be Able To

we use Be Able To in a similar way to can or could.

However, there are some important differences to remember. For example, because it is not possible to use can in the future tenses, we use Be Able To instead. Let’s look at two examples.

Can you finish the system updates?

Will you be able to finish the system updates?

Is there a difference in meaning between these two sentences? They mean more or less the same thing. However, there are subtle differences. Can you finish...?, could simply be an instruction, but it could also mean do you have the ability, do you know how to do it? 

Will you be able to...? means is it possible, or do you have the time? With this sentence, we assume that the person knows how to perform the system updates, so the question is only about possibility, rather than ability. 

Can and could express aptitudes or capabilities acquired with time. Be Able To is used to refer to abilities or inabilities that are both temporary or precise. As we saw before, can you…? refers to capability, whereas will you be able to…? refers to a precise situation. 

Let’s look at another example.

You won’t be able to use that particular software without upgrading your phone first.

Here, we use Be Able To to sound more polite. If we are talking to a customer, it doesn’t sound polite enough if we say:

You can’t use that particular software without upgrading your phone first.

It sounds too direct, like we are giving an order instead of offering a politely-worded solution to the problem. Can’t always sounds more emphatic than be able to.

You can use be able to in many situations when politeness is necessary.