Modal auxiliary verbs 2 – Necessity: must, have to, have got to, need, needn't

Analysis 1

What functions do mustand mustn't have in the sentences below?

  • rules and orders
  • strong encouragement
  • emphasizing a feeling

Where might you see or hear the examples? Who is the intended listener or reader?

All electronic appliances must be switched off during take-off and landing.

You mustn't take more than the prescribed dose.

You mustn't play on the building site – it's very dangerous. Do you understand?

You must come over for dinner. Are you busy next week?

It's the best book I've ever read. You must read it.

I must say I don't think that's a very good idea.

Analysis 2

Explain the use of must / mustn't, have to / don't have toand have / haven't got toto express necessity in the examples below. Consider these points:

  • Is the sentence likely to be written or spoken?
  • Does the authority come from the speaker or some other source?
  • Does the sentence relate to past, present or future?
  • Is the register more or less formal?
  • Is an adult talking to a child?
  • Are the consequences of not following the rule serious?

You must finish your homework before you watch TV.

Cars must not be parked here.

I must remember to send that application. The deadline is Friday.

You have to wear a tie and a white shirt.

You mustn't drive while you're taking these pills.

I'll be a few minutes late –I've got to go to the bank on the way.

I can stay out late tonight – I haven't got to work tomorrow.

You mustn't touch the electric plugs – you might get a shock.

You don't have to get a visa to visit Macau.

I had to wear school uniform until I was sixteen.

You'll have to finish your homework after dinner.

Necessity 2 : need to, don't need to and needn't

What is the difference in meaning between the following pairs of sentences?

You needn't come into the office tomorrow – you can work from home.

You don't need to / don't have tocome into the office on Fridays – you can work from home.

Ididn't need to bring any food as lunch was provided.

You needn't have brought a packed lunch – lunch is provided.

Modal auxiliary verbs 2 –Obligation and advice: should, ought to, be supposed to, had better

Compare the function of the use of should / shouldn't / ought to in the following examples.

Teachers should get a pay rise.

There shouldn't be so much violence on TV.

You should take some warm clothes – it'll be colder than you think.

You shouldn't drink the tap water.

You ought to take a grammar course at HKU SPACE.

They should be here soon.

Compare the use of obligation and advice words and phrases in the following pairs:

You should be more careful.

You should've been more careful.

You should see a doctor.

You'd better see a doctor.

We shouldn't make a noise.

We'd better not make a noise.

You shouldn't make personal calls at work.

You're not supposed to make personal calls at work.

You have to get your expenses claims in by the end of the month.

You're supposed to get your expenses claims in by the end of the month.

Answers

Modal auxiliary verbs 2 – Necessity: must, have to, have got to, need, needn't

What functions do mustand mustn't have in the sentences below?

  • rules and orders
  • strong encouragement
  • emphasizing a feeling

Where might you see or hear the examples? Who is the intended listener or reader?

All electronic appliances must be switched off during take-off and landing. / rules and orders
You mustn't take more than the prescribed dose. / rules and orders
You mustn't play on the building site – it's very dangerous. Do you understand? / rules and orders
You must come over for dinner. Are you busy next week? / strong encouragement
It's the best book I've ever read. You must read it. / strong encouragement
I must say I don't think that's a very good idea. / emphasizing a feeling

Analysis 2

Explain the use of must / mustn't, have to / don't have to and have / haven't got toto express necessity in the examples below. Consider these points:

  • Is the sentence likely to be written or spoken?
  • Does the authority come from the speaker or some other source?
  • Does the sentence relate to past, present or future?
  • Is the register more or less formal?
  • Is an adult talking to a child?
  • Are the consequences of not following the rule serious?

You must finish your homework before you watch TV. / Parent to child
Cars must not be parked here. / Written notice
I must remember to send that application. The deadline is Friday. / Strong reminder to self
You have to wear a tie and a white shirt. / Explaining what is necessary
You mustn't drive while you're taking these pills. / Strong rule – serious consequences if not followed
I'll be a few minutes late –I've got to go to the bank on the way. / Informal spoken
I can stay out late tonight – I haven't got to work tomorrow. / Informal spoken
You mustn't touch the electric plugs – you might get a shock. / Parent to child – serious consequences if not followed
You don't have to get a visa to visit Macau. / Explaining something that isn't necessary
I had to wear school uniform until I was sixteen. / Past – 'had to' is used for 'must' and 'have to'
You'll have to finish your homework after dinner. / Future – 'will have to' is used for 'must' and 'have to'.

Necessity 2 : need to, don't need to and needn't

What is the difference in meaning between the following pairs of sentences?

You needn't come into the office tomorrow – you can work from home.

You don't need to / don't have to come into the office on Fridays – you can work from home.

Needn't – what is necessary or not necessary on a particular occasion.

Don't need to – generally not necessary.

I didn't need to bring any food as lunch was provided.

It wasn't necessary to bring food so you didn't bring food.

You needn't have brought a packed lunch – lunch is provided.

It wasn't necessary to bring food but you brought some.

Modal auxiliary verbs 2 –Obligation and advice: should, ought to, be supposed to, had better

Compare the function of the use of should / shouldn't / ought to in the following examples.

Teachers should get a pay rise. / Something we think is a good idea – an opinion.
There shouldn't be so much violence on TV.
You should take some warm clothes – it'll be colder than you think. / Advice
You shouldn't drink the tap water.
You ought to take a grammar course at HKU SPACE.
They should be here soon. / Something that is likely – a degree of certainty relating to the future

Compare the use of obligation and advice words and phrases in the following pairs:

You should be more careful. / Advice – relates to the present.
You should've been more careful. / Criticism / regret relating to past actions.
You should see a doctor. / Advice.
You'd better see a doctor. / Stronger advice – more urgent.
We shouldn't make a noise. / Advice to self / group.
We'd better not make a noise. / Stronger advice to self / group.
You shouldn't make personal calls at work.
You're not supposed to make personal calls at work. / Explaining someone else's rule. This may serve as a gentle reminder, or suggest that the rule is not obeyed or strictly enforced.
You have to get your expenses claims in by the end of the month. / Explaining what is necessary.
You're supposed to get your expenses claims in by the end of the month. / Explaining someone else's rule. This may serve as a gentle reminder, or suggest that the rule is not obeyed or strictly enforced.