Modals of Ability

Form

Subject + can / am/is/are able to + Verb

She can speak three languages.

I am able to help you now.

Subject + can’t / am/is/are not able to + Verb

He can’t drive.

We are not able to attend the meeting.

Can + S + V? / Am/Is/Are + S + able to + V?

Can you swim?

Are you able to finish this today?

Subject + could / was/were able to + Verb

He could play piano as a child.

She was able to fix the car.

Subject + couldn’t / was/were not able to + Verb

I couldn’t find my keys yesterday.

They were not able to get tickets.

Could + S + V? / Was/Were + S + able to + V?

Could you understand the lesson?

Were they able to catch the train?

Subject + will be able to / have/has been able to + Verb

You will be able to speak better English soon.

She has been able to work remotely.

Subject + won’t be able to / haven’t/hasn’t been able to + Verb

I won’t be able to join the call.

He hasn’t been able to find a new job yet.

Will / Have/Has + S + be/been able to + V?

Will you be able to come to the party?

Has she been able to contact him?

Meanings

General or Inherent Ability

We use can (present) and could (past) to talk about a skill or a general ability. It describes what is generally possible for someone, not what they did on one specific occasion.

Present: She can play the guitar.

Past: When I was young, I could run very fast.

Ability in a Specific Past Situation

To talk about succeeding in a single, specific past event, we must use was/were able to. We do not use could.

Example: The team was able to win the match in the final minute. (Correct)
Incorrect: The team could win the match…

Exception: In negative sentences, couldn’t is common for both general and specific situations.

Example: I couldn’t open the jar.

Future Ability

Can and could do not have future forms. To talk about ability in the future, we must use the structure will be able to.

Example: After I fix my computer, I will be able to email you.

It is always incorrect to say “will can” or “will could”.

Incorrect: I will can help you tomorrow.

Incorrect: I will could help you tomorrow.

Permission & Possibility

Can and could are also commonly used to ask for permission or to talk about possibility. Could is generally more polite or formal than can.

Permission:

Can I use your phone?

Could we leave a few minutes early?

Possibility:

These roads can be very icy in winter.

It could rain this afternoon.