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Learning Objectives

2 minutes reading
✓
Use "must" for internal obligation and strong necessity
✓
Use "have to" for external obligation and rules
✓
Express prohibition with "mustn't" and "can't"
✓
Apply obligation language to policies and compliance
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Key for this lesson

Must = personal/internal obligation ("I must finish this"). Have to = external rule/obligation ("We have to follow company policy"). Mustn't = prohibition. Don't have to = not necessary.

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Grammar Explanation

4 minutes reading
Must / Have to

Obligation & Necessity

Must + base verb / Have to + base verb

Must: Personal obligation, strong feeling - "I must call the client."

Have to: External rules - "We have to wear badges."

alwaysrequiredmandatory
Mustn't / Don't have to

Prohibition vs No Necessity

Mustn't ≠ Don't have to

Mustn't: Prohibited - "You mustn't share passwords."

Don't have to: Not necessary - "You don't have to attend."

forbiddenoptionalprohibited
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Key Difference

Mustn't = DON'T DO IT (prohibition). Don't have to = you can if you want (no obligation). This is a common error!

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Context & Professional Usage

5 minutes reading

Obligation (Must / Have to)

📋Policies: "Employees must complete training."
🔒Compliance: "We have to follow GDPR regulations."
⏰Deadlines: "I have to submit the report by Friday."
👔Dress code: "Staff have to wear business attire."

Prohibition (Mustn't / Can't)

🚫Security: "You mustn't share your password."
📵Rules: "Employees can't use personal devices."
🤫Confidentiality: "You mustn't disclose client data."
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Business English Examples

6 minutes reading
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Correct Professional Usage

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"All employees must attend the safety briefing."

Strong internal requirement

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"We have to submit expenses within 30 days."

External company rule

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"You mustn't forward confidential emails."

Prohibition - not allowed

✓
"You don't have to work on weekends."

Not necessary (but you can)

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Common Business Mistakes

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"You don't have to smoke in the office."

Use: "You mustn't smoke..." (it's prohibited!)

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"I must to finish this report."

Use: "I must finish..." (no "to" after must)

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"She musts attend the meeting."

Use: "She must attend..." (no -s with modals)

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Professional Listening Exercise

6 minutes

Listen to an HR manager explaining company policies to new employees:

🎵Audio: New Employee Orientation
Ready
0:00 / 0:00
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Speed:

HR Manager:

"Welcome to the team. Let me explain some important company policies.

First, security. You must wear your ID badge at all times in the building. You mustn't let anyone follow you through security doors - everyone has to scan their own badge.

Regarding confidentiality, you mustn't share any client information externally. This is very important. If you're unsure about what you can share, you must check with your manager first.

Working hours are flexible. You don't have to arrive exactly at 9am, but you have to complete 40 hours per week. You must log your hours in the system every day.

For expenses, you have to submit receipts within 30 days. You don't have to get pre-approval for expenses under €50, but you must keep all receipts.

Finally, dress code. You don't have to wear formal business attire every day - smart casual is fine. But you must dress professionally when meeting clients."

Question 1: What must employees wear at all times?

Question 2: Do employees have to arrive exactly at 9am?

Question 3: Complete: "You _______ share any client information externally."

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Quick Comprehension Quiz

4 minutes
1

Smoking is prohibited in the office. Choose the correct form:

AYou don't have to smoke here.
BYou mustn't smoke here.
CYou shouldn't smoke here.
2

The meeting is optional. Choose the correct form:

AYou don't have to attend.
BYou mustn't attend.
CYou can't attend.
3

Company regulation: "All staff _____ complete the annual training."

Ahave to
Bdon't have to
Cmustn't
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Professional Practice Exercises

7 minutes

Exercise A: Complete with must, mustn't, have to, or don't have to

1. Employees _______ wear ID badges at all times. (required)

2. You _______ use your phone during meetings. (prohibited)

3. You _______ book a meeting room for informal chats. (not necessary)

4. All visitors _______ sign in at reception. (external rule)

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Speaking Preparation

4 minutes
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Preparation for Class

Practice explaining rules and obligations at your workplace.

📋 Task 1: Company Rules (1 min)

Describe rules at your workplace using must/have to/mustn't.

🔓 Task 2: Flexibility (2 min)

What don't you have to do at work? Discuss optional things.

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Summary

Must/Have to: obligation
Mustn't: prohibition
Don't have to: not necessary (optional)

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