Can
We use the auxiliary verb "can" in these situations:
Examples:
She can swim very well.
He can speak five languages.
Examples:
Mistakes can happen to anyone.
Friends can help you feel better when you're sad.
Examples:
You can't smoke here.
Can I take a photograph?
Examples:
Can you help me with my homework?
Can you open the window, please?
Let's take a look at the different forms of the auxiliary verb "can" in positive and negative statements and questions.
Positive
I can do ... .
You can do ... .
He can do ... .
She can do ... .
It can do ... .
We can do ... .
You can do ... .
They can do ... .
Negative
I cannot do ... . / I can't do ... .
You cannot do ... . / You can't do ... .
He cannot do ... . / He can't do ... .
She cannot do ... . / She can't do ... .
It cannot do ... . / It can't do ... .
We cannot do ... . / We can't do ... .
You cannot do ... . / You can't do ... .
They cannot do ... . / They can't do ... .
Positive Questions
Can I do ... ?
Can you do ... ?
Can he do ... ?
Can she do ... ?
Can it do ... ?
Can we do ... ?
Can you do... ?
Can they do ... ?
Negative Questions
Can I not do ...? / Can't I do ... ?
Can you not do ... ? / Can't you do ... ?
Can he not do ... ? / Can't he do ... ?
Can she not do ... ? / Can't she do ... ?
Can it not do ... ? / Can't it do ... ?
Can we not do ... ? / Can't we do ... ?
Can you not do ... ? / Can't you do ... ?
Can they not do ... ? / Can't they do ... ?
Short Answers
Yes, I can. / No, I can't.
Yes, you can. / No, you can't.
Yes, he can. / No, he can't.
Yes, she can. / No, she can't.
Yes, it can. / No, it can't.
Yes, we can. / No, we can't.
Yes, you can. / No, you can't.
Yes, they can. / No, they can't.
As you can see, the auxiliary verb "can" is used to make negative sentences and questions.
Examples:
+She can play the piano.
-She cannot / can't play the piano.
+?Can she play the piano?
-?Can't she play the piano? / Can she not play the piano?
Yes, she can. / No, she can't.
As you can see, after the auxiliary verb 'can,' we use the base form of a verb, which does not take either the third person singular "-s", "-ed", or "-ing", and we cannot put "to" before it either.
Example:
She cans plays the piano well.
Also, you can see that in negative sentences it is more common to write "cannot" as one word with no space in between.
Exercises
Complete each sentence with the correct form of "can" and a verb from the list below.
open | tell | see | play | use | catch
1I'm sorry, I ____ you on the weekend. I'm so busy.
I'm sorry, I can't see you on the weekend. I'm so busy.
2Excuse me, I think I'm lost. ____ I ____ your cell phone to call my parents?
Excuse me, I think I'm lost. Can I use your cell phone to call my parents?
3It's too hot. ____ I ____ the window?
It's too hot. Can I open the window?
4The dog is so smart. It ____ the ball when I throw it.
The dog is so smart. It can catch the ball when I throw it.
5We ____ together after school if you want.
We can play together after school if you want.
6____ you ____ me how to get to the library from here?
Can you tell me how to get to the library from here?