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.

Afirmative	Negative	Questions and short answers
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.

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").