Must, Must Not, & Do Not Have To

You must have a passport when you travel abroad

I must get to the parking lot of the train station by 7:30 am, otherwise I won’t get a parking spot. That parking lot fills up pretty quickly. There aren’t very many place to park near the train station. Even though there is a big parking lot for a nearby church, we must not park there. A lot of people who work later than I do have trouble finding a spot to park. Luckily, I don’t have to worry about that.

Today, I want to look at must, must not and do not have to. These can be confusing because the meanings are not as you may think. First, let’s look at must.

Must is used to show necessity. The grammar is must + base verb. Generally, when you must do something you have no choice:

• When you fly, you must have a passport.
• Drivers must stop at a red light.
• You must have a library card if you want to borrow books.

The negative form of necessity is do not have to. The grammar is do not have to + base verb. You can use do not have to when you want to show what is not necessary:

• When you take a train in the USA, you do not have to have a passport. Not, you must not have…
• Drivers do not have to stop at a green light.
• If you want to read a book in the library, you do not have to have a library card.

In English, must not is used to mean it is forbidden / it is not allowed / don’t do that, so the meaning is totally different from must. The grammar is must not + base verb.

• You must not smoke in this building. It means, smoking is not permitted.
• You must not drink and drive a car.
• You must not talk loudly in the library.