Practice
Ought to and must: understand the difference
Sign in to saveYou ought to save a copy of your work. You must show your pass at the door. Both forms guide someone, but the second sentence carries a stronger requirement.
Choose ought to for advice or a reasonable expectation and must for a strong requirement, necessity, or logical conclusion.
Read and practice
Read the examples and try the written questions in this guide. Listening recordings are not available for this lesson yet.
Try the written questions
You ought to check the address before you send the package. /juː ɔːt tə tʃek ði əˈdres bɪˈfɔː juː send ðə ˈpækɪdʒ/
The short answer
Use ought to for advice and likely expectations. Use must for a strong obligation, an essential need, or a conclusion that seems certain.
You ought to rest today, but you must take the medicine on time.
Why it works: Resting is advice. Taking the medicine is presented as necessary.
5 more examples
-
You ought to check the address before you send the package.
The speaker recommends a sensible action before sending the package.
Not this:You
must checkthe address before you send the package. What changes: Must makes the checking a firm requirement, perhaps because an error would cause a problem. -
All guests must wear a badge inside the building.
The sentence states a rule for everyone in the building.
Not this:All guests
ought to weara badge inside the building. What changes: Ought to sounds like advice, so it is weaker when the building has a real rule. -
The delivery ought to arrive this afternoon.
The speaker expects the delivery because of the available information.
Not this:The delivery
must arrivethis afternoon. What changes: Must can express a deadline or strong necessity, not a simple expectation. -
The lights are on, so Maya must be at home.
Must shows a confident conclusion from the evidence of the lights.
Not this:The lights are on, so Maya
ought to beat home. What changes: Ought to makes this an expectation, with more room for doubt. -
You ought not to share your password with anyone.
The speaker gives strong advice against an action.
Not this:You
must not shareyour password with anyone. What changes: Must not makes sharing forbidden, not simply unwise.
Read the full guide
First, ask what the speaker means. If the speaker is recommending a sensible action, ought to fits. If the speaker is stating a firm rule or a need that cannot be ignored, choose must. Must can also express a conclusion: after seeing wet umbrellas by the door, you might say that it must be raining outside.
Choose ought to for advice
Use ought to when you tell someone what you think is a good or sensible choice. The listener can usually choose differently, even when the advice matters. Ought to is close in meaning to should.
You ought to check the address before you send the package.
The sentence recommends checking. It does not state a rule from an authority.
I think you ought to speak to your manager first.
This is a recommendation about the next sensible step.
Which form gives advice: You ___ take a short break.
Use ought to: You ought to take a short break.
Use must for a firm rule or need
Use must when an action is required or necessary. A rule may come from an organization, a sign, or the speaker. Must makes the requirement stronger than ordinary advice.
All guests must wear a badge inside the building.
The badge is a condition of being in the building, so must fits.
You must keep this receipt for your records.
The speaker presents keeping the receipt as necessary.
Complete the rule: Employees ___ use the side entrance after 6 p.m.
Use must when the sentence states a firm workplace rule.
Use ought to for an expectation
Ought to can also say what you expect from a plan, schedule, or normal situation. It does not promise the result. It shows that the result seems likely if things happen as expected.
The delivery ought to arrive this afternoon.
The speaker expects an arrival, perhaps after checking the delivery schedule.
The new software ought to work after the update.
The expected result is not guaranteed, so ought to leaves room for a problem.
Which form fits a likely result after a repair: The screen ___ work now.
Use ought to when you mean that the screen is expected to work.
Use must for a confident conclusion
Must does not always give an order. It can show that the speaker has reached a strong conclusion from evidence. This use often appears with be: must be, must have been, or must be doing.
The lights are on, so Maya must be at home.
The lights give the speaker a reason to believe that Maya is home.
You have been traveling all day. You must be tired.
The long journey is evidence for a confident guess, not an instruction.
Choose the form for a strong guess: The café is closed, so they ___ be on vacation.
Use must be. The speaker is making a conclusion from the closed café.
Keep the negative meanings separate
A small change creates a large difference here. Must not means that an action is forbidden. Ought not to means that the speaker advises against it. Do not have to means there is no need to do it.
Visitors must not touch the paintings.
This is a prohibition. Touching the paintings is not allowed.
You do not have to print the email.
Printing is optional. The sentence does not forbid it.
Before you go
Remember this
Use ought to when you recommend an action or expect something to happen. Use must for a firm rule, a necessary action, or a conclusion that the evidence makes very likely. Check the negative carefully: must not means forbidden, while do not have to means unnecessary.
Practice with the written examples
You can practice with the written questions in the Learn tab. Each answer includes an explanation.
Try the written questionsListening test not available yet
This lesson does not have the recordings needed for a listening test. Use the written questions in the guide to check your understanding.
Try the written questionsQuestions about "Ought to and must: understand the difference"
What is the difference between ought to and must?
Use ought to when you recommend a sensible action or describe something you expect to happen. Use must when an action is required, necessary, or certain from the evidence. Must is usually stronger, while ought to leaves more room for personal choice or uncertainty.
You ought to check the address before you send the package.
Is ought to the same as should?
Ought to and should often give the same kind of advice, and should is more common in everyday conversation. Ought to can sound slightly more formal or more considered. Both can also describe what a speaker expects, but neither one guarantees the result.
You must check the address before you send the package.
Can must express a conclusion instead of a rule?
Yes. Use must when evidence makes a conclusion seem very likely. In The lights are on, so Maya must be at home, must does not give Maya an order. It shows the speaker's confident guess from the lights being on.
All guests must wear a badge inside the building.
What does must not mean?
Must not means that something is forbidden. It is different from do not have to. If you do not have to do something, it is optional. If you must not do it, you are not allowed to do it.
All guests ought to wear a badge inside the building.
How do I make ought to negative?
Use ought not to before the base verb: You ought not to share a password. Oughtn't to is also correct, but it is less common. This form gives advice against an action. It does not carry the same force as must not, which states a prohibition.
The delivery ought to arrive this afternoon.