1) What are modal verbs?
- Common modal verbs are 'Can', 'Could', 'May', 'Might', 'Will', 'Would', 'Shall', 'Should' and 'Must'. They are used to express ability, request, permission, advice, etc.
Examples:
I can swim. (Ability)
Could I have some tea, please? (Request)
You should send an email. (Advice)
- Modal verbs have the same form for all subjects and they are followed by the infinitive without 'to'.
Examples:
I can swim.
My brother can swim.
They can swim.
2) 'Can' and 'Can’t'
- We use 'can' and 'can’t' to talk about ability, possibility and impossibility in the present.
Examples:
She can speak several languages. (Ability)
They can’t dance very well. (Ability)
We can watch the match on my laptop. (Possibility)
We can’t watch the match on TV. (Impossibility)
- We use 'can' and 'can’t' to ask for, give or refuse permission.
Examples:
Can I go home now? (Ask for permission)
You can go home now. (Give permission)
You can’t go home yet. (Refuse permission)
- We use 'can' to make requests and offers.
Examples:
Can you help me with my homework? (Request)
Can I help you? (Offer)
I can do that for you if you like. (Offer)
3) 'Could' and 'Couldn’t'
- We use 'could' and 'couldn’t' to talk about ability, possibility and impossibility in the past.
Examples:
She could speak several languages. (Ability)
They couldn’t dance very well. (Ability)
We could watch the match on my laptop. (Possibility)
We couldn’t watch the match on TV. (Impossibility)
- We use 'could' to ask for permission or make a request politely in the present.
Examples:
Could I go home now? (Ask for permission politely)
Could you help me with my homework? (Make a request politely)
- We use 'could' to make offers and suggestions in the present.
Examples:
I could do it now, if you like. (Offer)
I could write a letter to the director. (Suggestion)
4) Negative forms of 'can' and 'could'
The negative form of 'can' is 'cannot' (can’t) and the negative form of 'could' is 'could not' (couldn’t).
Examples:
(+) She can speak several languages.
(-) She cannot speak several languages.
(+) We could watch the match on my laptop.
(-) We could not watch the match on my laptop.
5) Question forms of 'can' and 'could'
We make questions by putting the subject after 'can' and 'could'.
Examples:
(+) She can speak several languages.
(?) Can she speak several languages?
(+) We could watch the match on my laptop.
(?) Could we watch the match on my laptop?