Modals of Obligation

Learn have to, must, need to, mustn't, don't have to, and don't need to.

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Topic

What does it mean?

Use have to, must, and need to for obligation or necessity. Use mustn't for prohibition. Use don't have to and don't need to when something is not necessary.

I have to study.
You mustn't run here.
We need to listen.
You don't have to pay.
Big idea

Ask: necessary, forbidden, or optional?

NecessaryI have to wear a seat belt.I must do it.
ForbiddenYou mustn't touch the wire.Do not do it.
Not necessaryYou don't have to bring lunch.You may, but it is optional.
Have to

Use have to for rules and duties.

I have to do homework.It is my duty.Obligation.
She has to wear a uniform.It is a rule.Use has to with he/she/it.
Do we have to wait?Asking about a rule.Question form.
Must / mustn't

Use must for strong obligation and mustn't for prohibition.

You must listen.It is very important.Strong rule.
You mustn't shout.It is forbidden.Do not do it.
She must be careful.Strong advice or rule.Must + base verb.
Signal words

Clue words can help.

Obligation cluesrule, duty, school, law, importantUse have to, must, or need to.
Prohibition cluesdanger, forbidden, do not, noUse mustn't.
Optional cluesnot necessary, optional, already doneUse don't have to / don't need to.
Form reminder

Have to forms.

AffirmativeI have to go.
She has to study.have/has to + base verb
NegativeI don't have to go.
He doesn't have to study.not necessary
QuestionDo you have to go?
Does she have to study?Do/Does + subject + have to?
Form reminder

Need to forms.

NecessaryI need to practise.
They need to hurry.need to + base verb
Not necessaryI don't need to wait.
She doesn't need to come.optional / not required
QuestionDo we need to bring books?
Does he need to call?Do/Does + subject + need to?
Compare

Same idea, different strength.

I have to wear a uniform.It is a rule or duty.External rule.
I must wear a helmet.Very strong rule or personal feeling.Strong obligation.
I don't have to wear boots.It is not necessary.Optional.
Common mistake

Do not confuse mustn't and don't have to.

Mustn'tYou mustn't run in the lab.It is forbidden.
Don't have toYou don't have to run.It is not necessary.
Not correctShe musts go.
He doesn't has to go.Use base verb forms.
Sentence completion 1

Choose the correct form.

We ___ a uniform at school.

Sentence completion 2

Choose the correct form.

That wire is dangerous. You ___ it.

Sentence completion 3

Choose the correct question.

___ we have to bring our books?

MCQ 1

Which sentence means it is not necessary?

Choose the best sentence.

MCQ 2

Which sentence shows necessity?

Choose the best sentence.

Paragraph completion 1

Fill five blanks.

Choose the correct form. Think about obligation, prohibition, necessity, or no necessity.

Students on time.
You in the hospital.
Lunch is provided. You food.
It is very hot. We water.
Maha finished early. She tomorrow.
Test 1

Mixed question types of 5

Answer all five. Then tap Finish test to see your result sheet.

1. Sentence completion

Sara ___ for the test.

2. MCQ

Which sentence shows prohibition?

3. Type the answer

You ___ have to come early. It is optional.

4. Type the answer

We ___ practise before the show.

5. MCQ

Which question is correct?

Cumulative result sheet

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