Modal Verbs - Can, Could, Be Able To Explanation and Examples

Can, Could, Be Able To

Can, could and be able to are used to express a variety of ideas in English:

Ability/Lack of Ability

Present and Future:

can/can’t + base form of the verb

1.    Tom can write poetry very well.

2.    I can help you with that next week.

3.    Lisa can’t speak French.

am / is / are / will be + able to + base form of the verb
am not/ isn’t / aren’t/ won’t be + able to + base form of the verb

1.    Mike is able to solve complicated math equations with his mobile phone.

2.    The support team will be able to help you in about ten minutes.

3.    I won’t be able to visit you next summer.

Past:

could / couldn’t + base form of the verb

1.    When I was a child I could climb trees.

was / were + able to + base form of the verb
wasn’t / weren’t + able to + base form of the verb
hasn’t / haven’t + been able to + base form of the verb

1.    I wasn’t able to visit her in the hospital.

2.    He hasn’t been able to get in touch with the client yet.

Note: Can and could do not take an infinitive (to verb) and do not take the future auxiliary will.

·         Incorrect: I can to help you this afternoon.

·         Correct: I can help you this afternoon.

·         Correct: I will (I’ll) be able to help you this afternoon.

Possibility / Impossibility

can / can’t + base form of the verb

1.    You can catch that train at 10:43.

2.    He can’t see you right now. He’s on the phone. 

could + base form of the verb

1.    I could fly via Amsterdam if I leave the day before.

Ask Permission / Give Permission

Can + Subject + base form of the verb (informal)

1.    Can you lend me ten dollars?

Can + base form of the verb (informal)

1.    You can borrow my mobile phone.

Could + subject + base form of the verb (polite)

1.    Could I have your number?

2.    Could I talk to your supervisor please?

Make a suggestion – To make a suggestion use:

Could + base form of the verb (informal)

1.    You could take the tour of the castle tomorrow.

Exercises: Can, Could, Be able to

Fill in the correct form of can, could or be able to as in the examples.

1.    Ben could not help his little brother with his homework yesterday.

2.    Can I call you later tonight?

1.    _______ Tony run long distances when he was a boy?

2.    ______ you please call a tow truck for me? My car broke down. (polite)

3.    The students _______ to buy their textbooks today. The bookstore is all out of them.

4.    ______ you teach me how to fix my mobile phone? You’re so good at it.

5.    ______ you ______ reach the customer if you call him at 4:00 his time?

Answers:

1.    Could

2.    Could

3.    aren’t able

4.    Can

5.    Will/be able to