A practical english grammar - Vyssaja skola 1978

The modal CAN
Sound symbols

a) Physical or intellectual ability, present or future time

He can swim very fast.

Can you tell me the answer to this question?

I can give it to you tomorrow.

b) Permission

I’m sorry, sir (a policeman speaking), you can’t park there. You can go to the movies this afternoon if you want to.

It has long been taught that can is incorrectly used in this meaning; nevertheless, it occurs frequently in informal speech and is considered quite correct by most speakers nowadays in all except the most formal language. (See MAY.)

c) Possibility or likelihood

We don’t recommend planting this tree close to your house, because this species can reach a height of 100 feet.