Can Vs Be able to

CAN AND BE ABLE TO

Can and be able to are often interchangeable and you can usually use either one without a difference in meaning.  But not always.

Can is a  modal auxiliary verb that expresses general ability in the Present tense, or could for general ability in the Past tense.

Be able to is not a modal auxiliary verb, it’s just the verb “be” + the adverb “able” + the infinitive “to”. 

Present Ability. We use both can and be able to, but can is much more common:

✔ James can speak three languages.

✔ James is able to speak three languages.

Future Ability. We only use will be able to to talk about a future skill or ability that you don’t have yet, but you will have in the future. We never use can for an ability that you will only have in the future:

                       ✔ When I finish training I will be able to run a 5 minute mile.

                      ✘ When I finish training I can run a 5 minute mile.

We use either can or be able to when we are talking about decisions and future arrangements:

                       ✔ The doctor can see you next Monday.

                       ✔ The doctor is able to see you next Monday.

                       ✔ Mom can drive you to school tomorrow.

                       ✔ Mom is able to drive you to school tomorrow.