Must or Have to?

"Must" and "have to" are synonymous; they are interchangeable. It is equally correct to say "You have to be 18 to buy a lottery ticket" and "You must be 18 to buy a lottery ticket." (In the context that you have used them, at least.)

The difference is in the negative."You must not... " means that you are required to NOT do the thing specified. "You do not have to..." means that you can do the thing if you want to but you aren't required to.

"You must not drive without wearing a seat belt" means that you are prohibited from driving without one; È vietato.

"You don't have to bring a passport" means that you can bring it if you want, but it's not necessary; È un'opzione. Until Brexit goes through, anyway.

You have to be 16 to buy cigarettes.

If you don't pass the exams at school, you must repeat the year.

When you go to London or Paris, you don't have to bring (either "a" or "your") passport.

You have to be 18 to buy a lottery's lottery ticket.

You have to get an authorization (the more common word is "license") if you want to keep a dog.

You mustn't smoke in pubs or restaurants.

If you want to drive ("ride" is normally used for motorcycles, "drive" is used for cars) a motorcycle, you have to wear a helmet.

When there is an election, all the adults have to vote.

You have to be 18 to buy a pint of beer in a pub.

You mustn't go on a bike at night without lights.

If you are 17 and want to marry, you don't have to ask for permission to from your parents. (The permission comes FROM the parents TO you.)

You must put on the security seat or, less commonly, safety belt if you drive the car, but if you are a passenger you don't have to. Not true in many places (unless the passenger is in a bus), but it's a grammar exercise so OK...

Must or Have to?