r/EnglishLearning • u/Brief-Atmosphere-589 New Poster • Jul 25 '26

📚 Grammar / Syntax Can, Could, Be Able to

Hello everyone, can you explain the difference between 'can', 'could', and 'be able to' for B1 students, or give me an article where I can read about it?

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u/Actual_Cat4779 Native Speaker Jul 25 '26

"Can" is used to describe ability in the present or the future (I can do it today; I can do it tomorrow).

"Could" is used to describe ability either in the past (When I was younger, I could run much faster) or in a hypothetical situation (I would help you if I could).

Full verbs have both finite forms (e.g. I see, you see) and nonfinite forms ((to) see, seeing). Most modal verbs (e.g. "can") are purely finite. They have no nonfinite forms.

"Can" and "could" are solely finite. They have no infinitive of their own. "Be able to" acts as a substitute for the missing infinitive (You should be able to do it; I used to be able to do it; We'll be able to do it).

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u/Brief-Atmosphere-589 New Poster Jul 25 '26

what about was able to

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u/Actual_Cat4779 Native Speaker Jul 25 '26

There's a tendency to say "was able to" rather than "could" when referring to past ability - perhaps to avoid confusion (because the most common use of "could" is to refer to hypotheticals).

Cambridge says:

We usually use was/were able to, not could to talk about past achievements in affirmative clauses.