1. Modal verbs

Modal verbs

ELS VERBS MODALS

Els modals formen una classe especial de verbs que comparteixen algunes característiques amb els verbs auxiliars (be, have i do ).

Les característiques més importants dels verbs modals són:

1. No tenen un significat propi, sinó que només tenen sentit quan van amb un altre verb que els acompanya. Aquest altre verb sempre es posa en infinitiu (sense to ).

2. Només tenen una forma, que serveix tant per a referir-se al present com al futur. Només el verb can té una forma pel passat (could). Per expressar aquests verbs en formes verbals que no tenen (per exemple, en infinitiu, present perfect , etc.), cal utilitzar expressions alternatives amb el mateix significat (algunes d’aquestes formes apareixen al quadre de sota).

3. No afegeixen mai la –s pròpia de la 3ª persona del singular en present.

4. Formen la negació i la interrogació igual que els verbs auxiliars. És a dir, en la forma negativa s’afegeix not al verb; en la forma interrogativa, es fa la inversió de subjecte i verb.

Els verbs modals més utilitzats són els següents:

Ampliació modals

Exercises

1.1. Modals of advice, necessity, obligation and prohibition.

must / have 

Use

We use must to talk about a personal feeling of obligation to do something.

I must remember to post the letter today.

You must phone your grandmother tonight.

We use have to to talk about an obligation that is a fact, or a rule or law.

You have to be sixteen before you can leave school.

We have to revise for our exams next week.

We use don’t have to/doesn’t have to to talk about something that is not an obligation.

You don’t have to do any homework tonight.

We use mustn’t to say that something is prohibited.

You mustn’t smoke in this area.

We use had to to talk about a past obligation.

We had to get up at five o’clock this morning.

Form

must / mustn’t + infinitive

I must phone Sarah tonight.

have to / don’t have to / doesn’t have to

+ infinitive

We don’t have to get up early tomorrow.

had to + infinitive

John had to help his mother yesterday.

1.2. Modals of ability

Expressing ability

1. Present

We can also say 'I am able to run very fast' but we prefer 'can' because it is shorter:

I can run very fast.

2. Past affirmative

We use 'could' to speak in general:

I could run very fast, too.

We use 'was able to' to refer to a particular occasion. We are not speaking in general:

I could run very fast. That's why I was able to escape from the policeman.

We use 'could have' for something which was possible, but we didn't do. It is connected to the third conditional.

3. Past negative

There is no difference between 'couldn't' and 'wasn't able to'. 

I couldn't run fast.
I wasn't able to run fast.

4. Other ways of expressing ability

In any tense, we can emphasise that the activity was difficult by using 'manage to':

I managed to open the bottle.

In any tense, we can emphasise that we were successful by using 'succeed in + gerund':

I succeeded in winning the cup.

1.3. Modals of possibility and certainty

may, might, could, must,can’t

Use

We use may, might and could when we think something is possible in the present or future.

Certain diets may prevent cancer.

We use must when we think something is certain in the present or future.

He must be very ill. He’s been off work all week.

We use can’t when we think something is impossible in the present or future.

You can’t be hungry. You’ve just eaten a

huge pizza.

We use may have, might have, could have, must have and can’t have + past participle to make deductions about the past.

I’m not sure, but I think Jamie may have gone home.

Form

must/can’t/might/may/could + infinitive

They might go to France for their holidays, but they haven’t decided yet.

may have, might have, could have, must haveand can’t have + past participle

Jenny isn’t in her room. She must have gone out.

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4. Negative prefixes

A prefix is a group of letters (affixes) added in front of a word or a root of the word to change its meaning. A negative prefix is a prefix which carries a negative meaning 'not' , 'opposite of'.

Common negative prefixes in English are un-, im-, in-, il-, and ir-, and dis-. Some of these prefixes are only attached to a noun or an adjective while some are only attached to a verb. It is not possible to predict whether the negative prefix un-, in-, or dis- is used with a particular word. The correct form must be learned.

1. The negative prefix un-

This prefix is normally attached to an adjective or a noun to form an adjective or a noun.

It is important to distinguish the negative prefix un- 'not' from the prefix un- 'do the reverse of' which is normally attached to a verb. The resulting word remains a verb.

2. The negative prefixes in-, im-, il-, ir-

This prefix is normally attached to an adjective. The resulting word remains an adjective.

It is also important to distinguish the meaning of the prefix im- or in- 'not' from those carrying the meaning 'in, into' which forms a verb.

3. The negative prefix dis- 'not, opposite of, away'

This prefix is normally attached to a verb, an adjective or a noun. The resulting words can be a verb, an adjective or a noun.