Grammar · Free lesson
Mustn’t or don’t have to? A ban is not a choice
A workshop bans photography but provides notebooks. Visitors may bring their own notebooks if they want. Your instructions need to express those two different rules.
Professor Scott MendozaThe short answer
Mustn’t means you are not allowed to do something in a rule like You mustn’t take photos. Don’t have to means it is not necessary: You don’t have to bring a notebook. That second sentence is not a ban on notebooks.
Not allowed and not necessary are different messages.
Mustn’t is the short form of must not. For rules, it tells someone not to do an action. Don’t have to removes the requirement, not the permission. With he, she or a person’s name, use doesn’t have to, keeping have after doesn’t.
One rule and one optional action
You mustn’t take photos in this room.
You don’t have to bring a notebook; we provide one.
Nina doesn’t have to bring a notebook.
You don’t have to bring one does not mean You mustn’t bring one. The first leaves no obligation; the second prohibits it.
Choose the message before the form
Say what is prohibited
You mustn’t take photos.
Say what is unnecessary
You don’t have to bring a notebook.
Change the subject to Nina
Nina doesn’t have to bring a notebook.
Try it now
Read the rule, then choose.
Read all answers and explanations
Photography is prohibited in the room. Which instruction states the ban?
You mustn’t take photos.Mustn’t expresses the prohibition. Don’t have to only removes a requirement; must would require the photos.
Notebooks are provided. Bringing your own is allowed but optional. Which sentence expresses no requirement?
You don’t have to bring a notebook.Don’t have to means bringing one is unnecessary. Mustn’t would forbid it, and must would require it.
Nina may bring a notebook, but she does not need to. Choose the correct form.
Nina doesn’t have to bring one.Nina takes doesn’t in this pattern. After doesn’t, keep the base form have, not has.
Put it into practice
Correct the workshop instructions.
Photography is banned. Bringing a notebook is allowed but unnecessary because one is provided. Keep the ban and correct the second instruction.
You mustn’t take photos. You mustn’t bring a notebook because we provide one.
See a model answer
You mustn’t take photos. You don’t have to bring a notebook because we provide one.
A small change in the negative changes the instruction. The corrected message matches both workshop conditions.
A little more clarity
Common questions
A few useful details before you move on.
Does don’t have to always grant permission?
It says there is no obligation. It does not, by itself, settle every other rule. In our workshop example, the context separately says that bringing your own notebook is allowed.
You don’t have to bring a notebook.
Is must not different from mustn’t?
Mustn’t is the contracted form of must not. Both express the same prohibition in the rule shown here.
You must not take photos.
Take it into your day
Mustn’t: do not do it. Don’t have to: it is not required.
Your next step · Available on Udemy
Make your instructions say what you mean.
This page practices one important contrast in negative instructions. The English Grammar and English Speaking course includes a Must, May, Might section with Learn it, Review it, Use it and Practice it, within its wider work on modal verbs.
Explore the course English Master Course: English Grammar and English Speaking