Grammar-Quizzes › Verb Phrases › Verb Groups › Modals › Should vs. Must

Should vs. Must

Express advisability, necessity, and requirement

Wind turbine
 

 

Present - Should vs. Must

SHOULD

recommendedShould expresses advisability, a suggestion.  "It is advisable to..."  or "This is a suggestion… " It is weaker than must.  Should is followed by a plain form verb. 

SHOULD PLAIN FORM VERB

People should

protect the environment. It makes good sense.  

We should

select cars so that they are more fuel-efficient.

Customers should

bring re-usable bags when shopping.
MUST

obligationWe use must to express a stronger point of view.  "We need to..."  "We have to..." The modal must also expresses opinion, one person's point of view.
MUST PLAIN FORM VERB

We must

protect our environment, or our resources will disappear.

Engineers must

redesign engines so that they are more fuel-efficient.

Customers must

pay for paper bags if they do not bring their own bags when shopping.
 

fossil fuel – gasoline and similar fuels formed by natural processes; fuel resources taken from the earth

plain form – base form, simple form

See Modal Review  "Obligation" – for giving polite direct suggestions

 

 

 

 

Ought (to) / Have (to)

Advisability

 

Ought and Have

OUGHT (TO) / IT'S A GOOD IDEA

weaker wordingOught (to) acts very much like a modal except that it is used with an infinitival complement. The modal or the infinitive clause can be negated without much difference in meaning. The question form is not used very much. Ought expresses weaker advisability than have (to).

OUGHT INFINITIVAL FORM

You ought

to use your car less.

You ought not

to use your car so often.
(not advisable)

You ought

to not use your car so often.
(advisable not to use it.)

Ought you

to use your car so often?

It's a good idea

to leave your car in your garage.
HAVE

stronger wordingHave (to), a semi-modal, expresses necessity (strong advisability). However, it is unlike  other modals in its use of do as an auxiliary and its use of an infinitival complement. Negating the modal results in a different meaning from negating the infinitive clause.
HAVE INFINITIVAL FORM

You have

to use other forms of transportation occasionally.

You do not have

to drive.
(not required – You decide.)

You have

to not drive everyday.¹ 
(required not to – Don't)

Do you have

to drive everyday?

It is necessary

to drive less.
 

¹The infinitive is "split" with not.

ought / ought to (Huddleston 3 §2.5.4)

 

 

 

 
NOT REQUIRED

some freedomDon't have to expresses something that is not required. "medium–high freedom to act"   (You don't have to park on the street, but it would be nice if you did.)

You don't have to park on the street. (But it would be nice if you did. / Other options exist.)  medium to high "freedom to act"

He doesn't have to go to work everyday.  He can work from home on some days. (It's not necessary.)

We don't have to drive big cars. We can choose to buy smaller ones.

PROHIBITED

obligation– no freedomHave to not expresses something that is prohibited— strong opinion. When spoken, not is emphasized. "no freedom to act". (Do not park on the street.)

You have to not park on the street.  It's necessary not to.

He has to not miss a minute of work. He's an airplane flight controller.

We have to not drive big cars.
 

 

See Modal Review – freedom to act

 

 

 

 

Had Better

Strong Advisability

 

Had Better (correct) v. Had Better (error)

HAD BETTER

Had better refers to the immediate future and is used to give strong advice (in some cases threatening advice!)  It is more urgent than should or ought to. The had in had better does not behave like other auxiliary verbs.
FORM

You had better close the door open or (else) all the heat will go out.  
 
NEGATIVE

You had better not close the door or the cat will be trapped inside.
 

NEGATIVE QUESTION

Hadn't you better close the door?  (I think you'll agree you had better.) 

TENSE RESTRICTED TO FUTURE

You had better close the door. (future)

You had to close the door. (past requirement or necessity)

I thought it was a good idea to close the door. (reworded to past)
HAD BETTER ERRORS

Had does not change form for tense or person. It always refers to the near future. Had is followed by not in a negative question but not in an positive question. Had better is always followed by the plain form  (base) verb.
 HAD + BETTER + PLAIN FORM — ONLY!

*You have better close the door open or…

*He has better close the door open or…

*You had better  to close the door open or…

*You had better closing the door open or…
HAD BETTER → NOT

* You hadn't better close the door or the cat will be trapped.
POSITIVE QUESTION

*Had you better close the door? (not used)

*Had you better not close the door? (not used) 

TENSE NOT ADJUSTABLE WITHIN ANOTHER CLAUSE

*I thought you had better close the door.  

(I thought you needed to / should have / ought to have closed the door.)

*They had better leave before the hurricane arrived.

(They needed to leave before the hurricane arrived.)

 

Had better restricts meaning to future. No tense adjustment (backshifting) can be done when embedded within another clause (e.g.,  He said that we had better leave immediately.  He says that we had better leave immediately.)

Solution - lightbulb Pop-Q "Had Better"

 

 

 

 

Should, Had Better, Must

Relative Strength of Advisability

 

 

 

Advisability – Weak to Strong

MODAL / MODAL-LIKE  AUXILIARIES

Expressing advisability depends on social situations such as age (younger v. older), relationship (acquaintance v. friend v. family) working relationship (employee v. boss, student v. teacher, client v. salesperson) and sovereignty/authority (citizen v. king/leader).
WEAK— LESS DIRECT / PEER 

You should walk more often.  (plain form verb)

You ought to walk a more often. (infinitive)

Shouldn't you walk more often?
STRONGER—MORE DIRECT

You had better walk more often.

You really ought to walk more often.

*Hadn't you better walk more often?

*Oughtn't you walk more often?
STRONGEST—MOST DIRECT / AUTHORITY

You must walk more often.

You have to walk more often.
OTHER EXPRESSIONS

Other wording for advisability includes expressing personal opinion (manner, disposition, feeling, perspective), reasoning (logic, rules, ethics, norms), questions (inviting others to express opinion) and negative questions (persuading others to agree).
WEAK— LESS DIRECT / PEER

It's a good idea to walk more often.

Why don't you walk more often? 

Don't you think you should walk more often. 
STRONGER—MORE DIRECT

I suggest that you walk more often.

I am asking/urging you to walk more often.

For your own good, walk more.  (health)

Don't you think that you ought to walk more often?
STRONGEST—MOST DIRECT / AUTHORITY

It's necessary / imperaative / required that you walk more.

I demand / order / insist that you walk more.
 

Must cannot be weakened. 

direct – stating exactly what you want or think; imposing your will

indirect – stating what you want in a way that allows the other person to express his/her will (opinion, attitude, feeling, perspective); "escape" wording

peer  –  equal level of formality (informality); a friend, same age or rank

authority – parent (elder), teacher, doctor, officer ; unequal formality level  (peer [polite and often indirect] to authority [polite but direct]

priority – something that you think is important and that needs attention before anything else

Negative questions press the other person for agreement:  Shouldn't you walk more often?  (I think you should.)

 

 

 

 

Should have / Needed to

Advice that comes too late

 

 

Hypothetical Advice

PAST HYPOTHETICAL ADVICE

Should have or ought to have express options that were not taken in the past.  "It would have been a good idea, but it did not happen." We use these words to point out errors when reviewing a situation or event.                                                

We should have protected the environment (but we didn't.)

We ought to have protected the environment (but we didn't.)

*We had better protected the environment. (but we didn't.)

It would have been a good idea to protect the environment (but we didn't.)
PAST  NECESSITY / LATE ADVICE

Needed to or had to express the idea that something was necessary or required.  Had to  expresses an actual past event. With these words, we express opinion on the most important items requiring attention or concern.

We needed to protect the environment. 

(It was needed. Maybe we did. Maybe we didn't.)

We had to protect the environment.

(It was required. Likely, we did.)

*We must have protected the environment. (inference)

It was necessary that we protect the environment.

(It was required. Likely, we did.)
 

*not used

Also see Must have — inference, conclusion, deduction

 

 

 

 

Must vs. Is/Are To

Legal Requirement

Judge
 

 

Common vs. Legal Requirement

MUST

The modal must expresses a strong requirement. The timing is a future or near future.

You must go to the court house on Monday November 1.

He had better get there by 10 a.m. (no later)

We are supposed to keep these doors unlocked.

You need to pay Jim the $3,000 that you owe him.
IS / ARE TO

The verb be + infinitive expresses a legal requirement. "Legalese" (legal speak) appears on signs and in court documents.

You are to appear in court Monday November 1. (future)

He is to be in the court by 10 a.m. (future)

These doors are to be kept unlocked during business hours. (passive-routine)

You are to pay Mr James the $3,000 that you owe him. (near future)
 

 

 

 

 

 

Advice Modals

Word Order

 

 

Word Order Table

AUXILIARY VERB SUBJECT AUXILIARY VERB BARE / INFINITIVE COMPLEMENT
STATEMENT        

advisable

We 

should

select (plain form)

clearn-air vehicles. 

advisable

We 

ought

to select  (infinitive)

clearn-air vehicles. 

necessary

We 

need

to select 

clearn-air vehicles. 

necessary

We 

have

to select 

clearn-air vehicles. 

QUESTION        

Should

we 

 

select

clearn-air vehicles? 

Ought

we 

 

to select

clearn-air vehicles? 

Do

we 

need

to select 

clearn-air vehicles? 

Do

we 

have

to select 

clearn-air vehicles?
TAG QUESTION        

advisable

We 

should

select

clearn-air vehicles.

advisable

We 

ought

to select

clearn-air vehicles. 

necessary

We 

need

to select 

clearn-air vehicles. 

necessary

We 

have

to select 

clearn-air vehicles. 

NEGATIVE        

advisable

We 

shouldn't

select

clearn-air vehicles. 

advisable

We 

ought not

to select

clearn-air vehicles. 

necessary

We 

don't need

to select 

clearn-air vehicles. 

necessary

We 

don't have

to select 

clearn-air vehicles. 

W / ADVERB        

advisable

We 

should continually

select

clearn-air vehicles. 

advisable

We 

ought to knowledgeably

select

clearn-air vehicles. 

necessary

We 

need to carefully

select

clearn-air vehicles. 

necessary

We 

have to responsibly

select 

clearn-air vehicles. 

A tag question can also occur with a negative main sentence and a positive final question: They shouldn't do that, should they? (I don't think they should.) 

Related page: And so / too  

 

 

 

 

Practice 1

Office Collaboration (group work)

a confusing sign
 

 

Read the Modal Usage (with errors in peer to peer and peer to superior usage)

The conversation below concerns the "No" sign in the upper right.  Nick is the Project Manager (boss) ,  Anne is the Design Assistant (works for Nick) and  Ross is also a  Project Assistant (works for Nick).  Anne and Ross are peers (equal level)

Nick (boss): What do you think of this design?

Anne (assistant): I don't understand what it means.

Ross (assistant):  I don't get it either.  What is the image inside the circle?

Nick: Really? I guess we'd better change it then.

Ross: We ought to use a more easily recognizable image. 

Anne:  What are the little black circles? Flowers?

Nick: No, it's machinery, a danger point in a piece of equipment.

Ross: Then, shouldn't we ought to make the machine image more identifiable?

Ane: What is the little bird-like image on top.

Nick: It's a hand that is caught in the machinery. We'd better make that easier to recognize too.

Anne: You should remove the diagonal red line because it covers part of the image.

Ross:  It's necessary to add text too.

Nick: OK.  We ought to get back to work. We have to have this ready by 4:00 for the meeting with our client.

catch / caught (past tense)

client – customer; person who hires a service to be done

diagonal line – a straight line that joins two opposite corners of a flat shape, such as a square or a circle

recognizable (Adj) – easy to identify what it is

 

 

 

 

Decide whether the strength of the modal usage is correct  for the particular person to use.

  1. Select the option that best describes the sentence.
  2. Compare your response to the feedback by clicking the "Check" or the "Check 1-8" button.

 

1.
Nick (boss) : What do you think of this design?
Anne (assistant) : I don't understand what it means.
Ross (assistant):  I don't get it either.  What is the image inside the circle?
Nick: Really? I guess we'd better change it then.

   

2.
Ross: We ought to use a more easily recognizable image.

   

3.
Anne: What are the little black circles? Flowers?
Nick: No, it's machinery, a danger point in a piece of equipment.
Ross: Then, shouldn't we ought to make the machine image more identifiable?

   

4.
Nick: It's a hand that is caught in the machinery. We'd better make that easier to recognize too.

   

5.
Anne: You should remove the diagonal red line because it covers part of the image.

   

6.
Ross: It's necessary to add text too.

   

7.
Nick: OK.  We ought to get back to work.

   

8.
We have to have this ready by 4:00 for the meeting with our client.

   

 

 

Pinch Point sign revised

 

 

 

 

 

 

Practice 2

Store Return Policy

policy
 

 

Read the Context

Before you buy something, you (try) it on. You (consider) carefully whether the item of clothing is right for you.  Sometimes,  (it's…) to take something home and try it on with other things, such as a jacket or shoes. If you decide the item is not right for you, you (not-keep) it. However, you (remove) the tags. You (place) the item back into its bag so that it will stay clean and can be resold. When you return to the store, you (have) the sales receipt.

You also (return) the item  within the time allowed. The store (accept) the item back without much complaint. The store (return) your money. However, it might just offer store credit. If you are unhappy with store credit, then you (ask) about the return policy when you bought it. The policy that was written on the back of your receipt informed you what you (do) for a cash refund.

allowed – permitted

complaint (N) – saying that one is unhappy or annoyed

inform (V) – state clearly and plainly in detail

refund (V) – return of money for the return of an item

 

 

 

 

Select the degree of advisability.

  1. Select the response from the list that best completes the sentence. 
  2. Compare your response to the feedback by clicking the "Check" or the "Check 9-20" button.

 

9.

10.

11.

12.

13.

14.

15.

16.

17.

18.

19.

20.