MODALS

PROBABILITY, ABILITY, OBLIGATION AND ADVICE, PERMISSION, HABITS

Modals are different from normal verbs:

1: They don't use an 's' for the third person singular.

2: They make questions by inversion ('she can go' becomes 'can she go?').

3: They are followed directly by the infinitive of another verb (without 'to').

4: They can form many verb tenses.

1.- Probability:
First, they can be used when we want to say how sure we are that something happened / is happening /will happen.

We often call these 'modals of deduction' or 'speculation' or 'certainty' or 'probability'.

For example:

• It's snowing, so it must be very cold outside.
• I don't know where John is. He could have missed the train.
• This bill can't be right. £200 for two cups of coffee!

A. Probability with “must / might / could / may / can't”
• must + infinitive
• might / might not + infinitive
• could / could not + infinitive
• may / may not + infinitive
• can't + infinitive

For example:
I am waiting for Julie with another friend, David.

I ask: 'Where is Julie?'

David guesses:
• 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.

Remember 'must have done' is a modal verb of deduction or speculation, not obligation in the past.

For example: Julie must have left. Her coat's not here

B. Probability with “Will / won't”

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

• She'll be at work now.
• The underground will be very busy now (not: 'should be').

C. Probability with “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').

2.- Ability
We use 'can' and 'could' to talk about a skill or ability.

For example:

• She can speak six languages.
• My grandfather could play golf very well.
• I can't drive.

A. Ability in the Present:
can / can't (for both general and specific ability)

• I can play the piano.
• She can speak English.
• He can't drive – he's too tired.
• We can't come now.

B. Ability in the Past:
could / couldn't (for general ability)

• I could read when I was four.
• She could speak French when she was a child, but now she has forgotten it.
• He couldn't dance at all until he took lessons.
• My grandfather couldn't swim.

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

• When the computer crashed yesterday, I was able to fix it.(not 'I could fix it')
• She was able to pass the exam, even though she hadn't studied much.(not 'she could pass')
• He called us because he couldn't find the house.
• I couldn't open the window.

could + have + past participle (an ability someone had in the past, but didn't use)

• I could have played the piano well but I didn't practise enough. (podría haber... pero...)
• We could have come earlier.
• She could have studied law, but she preferred to become a secretary.

C. Ability in the Future:
will / won't be able to (general ability)
• At the end of the course, you will be able to make your own website.
• He won't be able to speak Japanese in a week! It will take months.

can / can't (specific ability)
• I can help you tomorrow
• I can't come to the party

3. Obligation and Advice

We can use verbs such as 'must' or 'should' to say when something is necessary or unnecessary, or to give advice.
For example:
• Children must do their homework.
• We have to wear a uniform at work.
• You should stop smoking.

Be careful about the difference between mustn't and don't have to!
Mustn't means it's not allowed, or it's a bad idea:

• You mustn't eat so much chocolate, you'll be sick

Don't have to means you don't need to do something, but it's fine if you want to do it:
• I don't have to get up early at the weekend (of course, if I want to get up early, that's fine, but I can stay in bed if I want).

4. Permission

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

For example:

• Could I leave early today, please?
• You may not use the car tonight.
• Can we swim in the lake?

5. Habits

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

For example:

• When I lived in Italy, we would often eat in the restaurant next to my flat.
• John will always be late!

6.- MODAL PERFECTS.

Using modal verbs to talk about the past:
must / might / could / may / can't + have + past participle
• must have + past participle
• might / might not have + past participle
• could / couldn't have + past participle
• may / may not have + past participle
• can't have + past participle

For example:
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.

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

Could

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

• Prices could be high in the sixteenth century.
 

Could

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

• Prices could be high in the sixteenth century.

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)