Permission and possibility: can/can't

CAN / CAN'T shows ability, inability, request, permission, possibility, and inappropriateness. In this unit we will focus in the permission and posibility.

 
You can park here
You can't cross when the light is red.
Can I park here? Yes, you can. But you have to pay at the parking metter.
 
You can go shopping in the city
You can't take the bus with your dog
Can I ride my bike here? No, you can't. It's too dangerous.
 
You can take money out at the ATM
You can't drive in this street. It's for bicycles only
Can I smoke here? No, you can't. We are in the underground station.

 

traffic signs

Negative form of CAN is either "cannot" or "can not" and its negative contraction is "Can't".

You can't smoke here. It refers to people in general and not particulaty used (unless we are using the pronoun "you").