Birds can fly. Birds can fly.
Can is a modal auxiliary verb which has different uses.
Affirmative: subject + 'can' + bare infinitive
I can swim.
Negative: subject + 'can' + 'not' + bare infinitive
I cannot swim. I can't swim.
Interrogative: 'can'+ subject + bare infinitive
Can you swim?
Note that like other modal auxiliaries, can has no infinitive and we use the same form with 'I', 'you', 'he', 'she', 'it', 'we' and 'they'.
'Do' is not used for negative or interrogative sentences.
Cannot
In the negative, we use cannot in formal written English. It is rare in conversation unless we use it for insistence. For example: These instructions are too complicated. I cannot understand them.
=====Uses=====
| Use | Examples |
|
Ability
|
She can speak four languages. She is ill so she can't play tennis at the moment. Can you swim?
|
|
Possibility
|
Sorry, I can't meet you today. I'm too busy. But I can see you tomorrow. Can you work on Saturday? Rachel's on holiday.
|
|
Permission |
'Can I leave early today?' 'Yes, you can, no problem.' You can't watch TV before you do your homework.
|
|
Requests
|
Can I have the tomato soup and a steak? Can you help me with this? Can you tell me how to get to the station?
|
|
Offers |
Hello, can I help you? Can we take you to the station?
|
=====Examples=====
|
He can drive!
|
Yes, I can have lunch with you - I'm free. |
|
Please can I go to the party? No, you cannot. You're too young! |
Can you take a message? |
|
Can I get you something to drink? |
|
