The word ‘carton’ is confusing in English. It is not, like in Czech, the box material in which you get, for example, your new pair of shoes. That is called cardboard. Thick paper is called ‘card’ and the thicker one used for boxes is called ‘cardboard’.
A carton is a box for liquid, for example, a carton of milk, or – the homeless favourite – a carton of wine. We also use the word for cigarettes when there are 10 packs together. At Duty Free, you buy a carton of cigarettes.
And one more thing since teachers get asked this – if there are several cartons of milk together, we do not use a carton of cartons! That is far too confusing. Instead, we are likely to simply say “6 cartons of milk”, or “a six-pack of milk”.
Here’s a conversation about recycling using the correct terms:
A: I need to take these cardboard boxes to the recycling bin. Could you pass me those milk cartons also?
B: Sure, I actually buy my milk in a bottle rather than a carton, it seems somehow healthier!