Can I use "can" instead of "be able to" here? What are the different ways to use "be able to" and "can"?
Native speaker’s answer
Rebecca
Firstly, due to the structure of this sentence, we absolutely cannot replace "be able to" with "can". This sentence is talking about future abilities. 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, whether in the negative form (as here with "never") or in the positive. We never use "can" for an ability that you will only have in the future. Ex: I will be able to see better with my new glasses. Ex: I'll never be able to understand algebra. "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”. So for the present tense ability, we can use either "can" or "be able to", although "can" is generally more common as it feels less formal. Ex: I can speak three languages. Ex: I am able to speak three languages.
