Modal verbs of probability

Modal verbs of probability

by Mario Medina

​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 sure we are.

​Modal verbs for probability in the present

​

​must / might / could / may / can't + infinitive

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​For example:

​I am waiting for Julie with another friend, David.I ask: 'Where is Julie? 'David guesses:

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​She must be on the bus. (I'm fairly sure this is a good guess)

​She might come soon. (maybe)

​She could be lost. (maybe)

​She may be in the wrong room. (maybe)

​She can't be at home. (I'm fairly sure this isn't true)

​

​Notice that the opposite of 'must' is 'can't in this case.

​Modal verbs for probability in the present

​

​Will / won't

​

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

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​She'll be at work now.

​Modal verbs for probability in the present

Should / shouldn't

​

Should and shouldn't are used to make an assumption about what is probably true, if everything is as we expect:

​​

​They should be there by now.

​It shouldn't take long to drive here.

​

​This use of should isn't usually used for negative events. Instead, it's a better idea to use will:

​The underground will be very busy now (not: 'should be').

​Modal verbs for probability in the present

Can

​

Can is used for something that is generally possible, something we know sometimes happens:

​

​Prices can be high in London.

​

​Can is not used to talk about specific possibilities:

​

He could be on the bus (not: 'can be').

Multiple Choice

You use this modal to say maybe.

• must

• might

• could

• can

Multiple Select

You use this modal to say maybe.

• must

• might

• could

• can

Multiple Choice

You use this modal to say you are fairly sure it is not true.

• must

• might

• could

• can't

Multiple Choice

You use this modal to make an assumption about what is probably true

• must

• might

• could

• should

Multiple Choice

You use this modal to talk about specific possibilities

• must

• might

• could

• should

Open Ended

Write 1 sentence using could for probability in the present.

Open Ended

Write 1 sentence using can't for probability in the present.

Open Ended

Write 1 sentence using may for probability in the present.

Open Ended

Write 1 sentence using must for probability in the present.

​Modal verbs for probability in the past.

​must / might / could / may / can't + have + past participle

​

​You: Where was Julie last night?

​David:

​She must have forgotten about our date.

​She might have worked late.

​She could have taken the wrong bus.

​She may have felt ill.

​She can't have stayed at home

​Modal verbs for probability in the past.

Will / won't + have + past participle

​

​Will and won't / will not + have + past participle are used for past certainty (compare with present use of 'will' above):

​

​The parcel will have arrived before now.

​Modal verbs for probability in the past.

Should + have + past participle

​

Should + have + past participle can be used to make an assumption about something that has probably happened, if everything is as we expect (compare with present use of 'should' above):

​

​The train should have left by now

​Modal verbs for probability in the past.

Could

​

We can use could + infinitive to talk about a general possibility in the past (compare with the use of 'can' above):

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​Prices could be high in the sixteenth century.

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​This is not used to talk about specific possibilites in the past (instead we use could + have + past participle):

​

​He could have been working late (not: 'could be'. As this is a specific possiblity, 'could be' is present tense)