Modal verbs: Permission, Obligation, Prohibition, Necessity
Master advanced modal verbs to express rules, duties, and permissions.
- check_circleI can express obligation and necessity using must, have to, and need to.
- check_circleI can talk about permission using can, could, and may.
- check_circleI can explain prohibitions using must not and can't.
Discover
Meet today's English in a real situation — no rules yet. Read it once and try to guess the pattern in the words in bold. Underlined words open a short definition.
Sarah: Welcome to the team, David! Let me go over some office rules. First, you must wear your ID badge at all times. It’s a strict security requirement.
David: Understood. What about the dress code? Do I have to wear a suit?
Sarah: No, you don’t have to wear a suit. Business casual is fine. However, you must not wear ripped jeans or flip-flops.
David: Makes sense. Can I work from home sometimes?
Sarah: You may work remotely on Fridays, but you need to get approval from your manager beforehand. It’s a nice perk.
David: That sounds great. Are there any other rules I should know?
Sarah: Well, you can’t use the executive parking lot, and you have to attend the weekly team meetings. If you need any stationery, you don’t need to buy it yourself; you can request it from the supply room.
David: Got it. Thanks for the overview!
Learn
Now the rules behind what you just saw — explained simply, with examples. Underlined words open a short definition — hover on desktop, tap on a phone.
In professional and academic settings, using the correct modal verbs to express what is allowed, required, or forbidden is crucial.
Permission
To talk about permission, we use can, could, and may.
- Can I use your laptop for a minute? (Informal)
- Could we reschedule the meeting to 3 PM? (More polite)
- You may leave the room when you finish the exam. (Formal)
Obligation and Necessity
When we talk about rules or things that are necessary, we usually use must and have to.
Use must for internal obligations (you feel it’s necessary) or formal written rules. Use have to for external obligations (someone else made the rule).
- I must remember to call my mother on her birthday. (Internal)
- All passengers must fasten their seatbelts. (Formal rule)
- I have to wear a uniform to work. (External obligation)
We can also use need to when an action is necessary for a specific purpose.
- I need to renew my passport before the trip.
Prohibition
To say that something is NOT allowed, we use must not (mustn’t) or can’t.
Do not use “don’t have to” for prohibition! “Don’t have to” means something is not necessary, but you can do it if you want (lack of obligation).
- You must not park here. (It is prohibited)
- You can’t enter the restricted area. (It is not allowed)
- You don’t have to attend the meeting. (It is optional)
Lack of Necessity
When there is no obligation to do something, use don’t have to, don’t need to, or needn’t.
- You don’t have to wear a tie to the office on Fridays.
- We needn’t rush; the flight is delayed. (More formal)
It’s important to understand the nuance between these modals to avoid misunderstandings.
- Permission: can, could, may
- Obligation: must, have to
- Necessity: need to
- Prohibition: must not, can’t
- No obligation: don’t have to, don’t need to, needn’t
Practice
Try it yourself. You'll see right away whether you got it right, plus a short explanation of why.
Use It
Now make the language yours in a real task. Use the prompt below — the editor keeps a simple word count, and nothing is saved or graded.
Before you finish — be honest. Can you do these now?