Can, Be able to (Intermediate)

The difference between Can and Be able to?
Can and Be able to both express an ability or possibility

Can (past tense: could) is only used in the present tense or the past tense; Be able to can be used for all tenses. This is because "can" and "could" are modal auxiliary verbs; therefore they can only be used in the present or past tense.

Note that could does not represent the past, it can show a general ability to do something: He could swim (It means he can swim now, not in the past!)
"Could" is used in a similar way to "may" to show courtesy: Could I have a cup of coffee? Sure, you can!
"Could" can also be used to show uncertainty: He couldn't do that bad in the exam.

"Be able to" can be used in the past tense "was/were able to" to show successfully accomplished something: He was able to phone him in the end = He managed to phone him in the end.

Can/Could have no infinitive form, so you can use "to be able to" instead.

In the negative, wasn't/weren't or couldn't are both correct.

Robbie Elden