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Modal Verbs of Probability

Click here for all the exercises about modal verbs

We can use these modal verbs (also called modals of deduction, speculation or certainty)when we want to make a guess about something. We choose the verb depending on how surewe are.

1: Talking about the present:

must / might / could / may / can't

• must + infinitive

• might might not + infinitive

• could could not + infinitive

• may may not + infinitive

• can't + infinitive

!or example"

# am waiting for $ulie with another friend, %avid.# ask" &Where is $ulie'&%avid guesses"

• he must be on the bus. (#&m fairly sure this is a good guess)

• he might come soon. (maybe)

• he could be lost. (maybe)

• he may be in the wrong room. (maybe)

• he can't be at home. (#&m fairly sure this isn&t true)

otice that the opposite of 'must & is &can't in this case.

Will / won't

We use will and won't when we are very sure"

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• he&ll be at work now.

hould / shouldn't

hould and shouldn't are used to make an assumption about what is probably true, ifeverything is as we expect"

• *hey should be there by now.

• #t shouldn&t take long to drive here.

*his use of should isn&t usually used for negative events. #nstead, it&s a better idea to use will "

• *he underground will be very busy now (not" &should be&).

!an

!an is used for something that is generally possible, something we know sometimeshappens"

• rices can be high in ondon.

!an is not used to talk about specific possibilities"

• -e could be on the bus (not" &can be&).

": #sing modal $erbs to talk about the past:

must / might / could / may / can't % ha$e % past participle

(Click here to review how to make the past participle )

• must ha$e + past participle

• might might not ha$e + past participle

• could couldn't ha$e + past participle

• may may not ha$e + past participle

• can't ha$e + past participle

!or example"

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ou" Where was $ulie last night'%avid"

• he must ha$e forgotten about our date.

• he might ha$e worked late.

• he could ha$e taken the wrong bus.

• he may ha$e felt ill.

• he can't ha$e stayed at home.

Will / won't % ha$e % past participle

Will and won't / will not % ha$e % past participle are used for past certainty (compare with present use of &will& above)"

• *he parcel will have arrived before now.

hould % ha$e % past participle

hould % ha$e % past participle can be used to make an assumption about something thathas probably happened, if everything is as we expect (compare with present use of &should&above)"

• *he train should have left by now

!ould

We can use could % infiniti$e to talk about a general possibility in the past (compare with theuse of &can& above)"

• rices could be high in the sixteenth century.

*his is not used to talk about specific possibilites in the past (instead we use could % ha$e %past participle )"

• He could have been working late (not: 'could be'. As this is a specifcpossiblity, 'could be' is present tense

&bility

We use &can& and &could& to talk about a skill or ability.

!or example"

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• he can speak six languages.

• /y grandfather could play golf very well.

• # can't dri$e

Present:

can / can't (for both general and specific ability)

• # can play the piano.

• he can speak 0nglish.

• -e can&t drive 1 he&s too tired.

• We can&t come now.

Past:

could / couldn't (for general ability)

• # could read when # was four.

• he could speak !rench when she was a child, but now she has forgotten it.

• -e couldn&t dance at all until he took lessons.

• /y grandfather couldn&t swim.

was able to / couldn't (for specific ability)

• When the computer crashed yesterday, # was able to fix it.(not &# could fix it&)

• he was able to pass the exam, even though she hadn&t studied much.(not &she could

pass&)

• -e called us because he couldn&t find the house.

• # couldn&t open the window.

could % ha$e % past participle (an ability someone had in the past* but didn't use)

• # could have played the piano well but # didn&t practise enough.

•

We could have come earlier.

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• he could have studied law, but she preferred to become a secretary.

+uture:

will / won't be able to (general ability)

• 2t the end of the course, you will be able to make your own website.

• -e won&t be able to speak $apanese in a week3 #t will take months.

can / can't (specific ability)

• # can help you tomorrow

• # can&t come to the party

,bligation and &d$ice

We can use verbs such as &must& or &should& to say when something is necessary orunnecessary, or to give advice.

!or example"

• Children must do their homework.

•

We ha$e to wear a uniform at work.

• ou should stop smoking.

We can use ha$e to % infiniti$e , must % infiniti$e and should % infiniti$e to expressobligation (something you have to do).

Present Positi$e -egati$e

have to don&t have to

strong obligation (possibly fromoutside)

• Children have to go toschool.

(sometimes &have got to&)

no obligation

• # don&t have to work onundays.

• ou don&t have to eatanything you don&t like.

must mustn&t strong obligation (possibly basedon the speaker&s opinion)

negative obligation

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• # must study today. • ou mustn&t smoke here.

should shouldn&t

mild obligation or advice

• ou should save somemoney.

mild negative obligation or advice

• ou shouldn&t smoke somuch.

4e careful about the difference between mustn't and don't ha$e to 3Mustn't means it&s not allowed, or it&s a bad idea"

• ou mustn&t eat so much chocolate, you&ll be sick

.on't ha$e to means you don&t need to do something, but it&s fine if you want to do it"

• # don&t have to get up early at the weekend(of course, if # want to get up early, that&sfine, but # can stay in bed if # want).

Past Positi$e -egati$e

had to didn&thave to

obligation in the past

• # had to wear a school

uniform when # was a child.

no obligation in the past

• We didn&t have to go to

school on aturdays.

must5 changes to &had to& 6

should have + pp shouldn&t have

+ pp

a past action which didn&t happen"the advice regret is too late

• ou should have gone to bed earlier, now you havemissed the train.

a past action which didn&t happen"the advice regret is too late

• ou shouldn&t have takenthat 7ob., it was a bad idea.

5 8emember 'must ha$e done & is a modal verb of deduction or speculation, not obligation inthe past. !or example" $ulie must have left. -er coat&s not here. ee modals of probabilty formore information.

Permission

We can use verbs such as &can&, &could& and &may& to ask for and give permission. We also usemodal verbs to say something is not allowed.

!or example"

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• !ould lea$e early today, please'

• ou may not use the car tonight.

• !an we swim in the lake'

0abits

We can use &will& and &would& to talk about habits or things we usually do, or did in the past.

!or example"

• When # lived in #taly, we would often eat in the restaurant next to my flat.

• $ohn will always be late3