I Swear English › Modal Verbs › Can, Could and Be Able To
How to form the can, could and be able to
Different tenses with the verb can:
Can is present, could is both past and conditional. There are no other parts of this modal verb. To make other tenses we use the verb to be able to.
Infinitive - to be able to
Present - I can or I am able to, he can or he is able to
Future - I will be able to, I am going to be able to
Past - I could or I was able to, you could or you were able to
Present Perfect - I have been able to, he has been able to
Conditional - I could or I would be able to
Conditional Perfect - I could have or I would have been able to
Imperfect subjunctive - If I could or if I were able to
Gerund - being able to
Participle - been able to
The following video explains can, could and to be able to:
When to use it
- Can — ability and possibility now. I can swim. Can you help?
- Could — past ability, and polite requests. I could read at four. Could you pass the salt?
- Be able to — ability in any tense, where can/could don't fit. I'll be able to drive soon. I haven't been able to sleep.
Signal words & time expressions: now, when I was young, in the future, one day
Watch the video lesson
Video transcript
Common mistakes to avoid
| Not quite… | Better |
|---|---|
| I | I can swim. — modal verbs are followed by the base verb, with no to. |
| Yesterday I | Yesterday I was able to finish the report. — for a single past achievement, prefer was able to. |
Frequently asked questions
When must I use ‘be able to’?
When there is no modal form available — after another modal, in the perfect, or in the future: You might be able to…, I've been able to…, I'll be able to…
‘Could’ or ‘was able to’ for the past?
Use could for a general past ability; use was/were able to for managing to do one specific thing on one occasion.
Continue the course
This lesson is part of our free English Modal Verbs course — work through it in order or jump to what you need next.