Modals of obligation and prohibition help you express rules and necessities clearly. They are crucial in formal writing and speaking to convey what is required or forbidden. In this lesson, you'll learn how to use these modals correctly to ensure your message is understood as intended.
Examples
Example 1
IncorrectEmployees must to complete the training by Friday.
BetterEmployees must complete the training by Friday.
"Must" is followed by the base verb without "to" to express obligation.
Example 2
IncorrectVisitors cannot to enter the restricted area.
BetterVisitors cannot enter the restricted area.
"Cannot" is used without "to" to indicate prohibition.
How It Works
Meaning
Modals for obligation and prohibition express rules and necessities. They indicate what actions are required or forbidden. Common modals for obligation include must and have to, while must not and cannot express prohibition.
These modals are essential for clear communication in formal and informal settings, especially at the B2 level, where precision in expressing rules and expectations is important.
Use it when
- Expressing a rule or requirement, such as in workplace policies.
- Stating prohibitions in formal documents or instructions.
- Communicating expectations in academic or professional contexts.
- Giving clear instructions to ensure compliance.
See it
Quick rules
- Use must or have to for strong obligations.
- Use must not or cannot for prohibitions.
- Do not add "to" after modals when using the base verb.
- Ensure the modal matches the level of necessity or prohibition intended.
Common Mistakes
Common problem 1
using "to" after a modal verb
WeakYou must to attend the meeting on time.
StrongYou must attend the meeting on time.
Fix: Use the base verb directly after the modal.
Common problem 2
using the wrong modal for prohibition
WeakYou should not smoke in this area.
StrongYou must not smoke in this area.
Fix: Use "must not" for strong prohibitions.
Practice Lab
Practice
Identify the correct modal form for obligation and prohibition, then apply it in sentences.
Score: 0/3
Focus on the correct use of modals to express obligation and prohibition accurately.
1. Quick pick
Select the sentence that correctly uses a modal for prohibition.
2. Build it
Put this obligation sentence in the correct order.
Tap a chunk to move it down. Tap it again to send it back.
3. Final sort
Mark each sentence as correct or needing a fix.
You must submit the report by Monday.
You must to submit the report by Monday.
Guests must not enter the restricted area.
Guests must to not enter the restricted area.
Why It Matters
🎯 Why it matters: Using the correct modals for obligation and prohibition ensures that your instructions and rules are clear and respected. This precision is essential in professional, academic, and everyday contexts where clarity and compliance are critical.
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