Modal verbs

Modal verbs are special verbs. They don’t usually need an auxiliar as they usually act as auxiliaries, they go before the verb , they don’t have all their forms and they can express different things: ability, permission, prohibition, possibility or probability, deduction and certainty.

AbilityTo express ability we use can

I can ride a bikeI can’t drive a car

The past and conditional forms of can are could

When I was young I could jump over that fence

The infinitive form of can is to be able to, so we say

I would like to be able to flyI have never been able to dance

Permission• In questions I can use can or may, the second is

more formal than the firstMay I use your phone, please?

• In general we use can to express permission, so sometimes it’s difficult to know whether we are refering to ability or permission.I can ride a motorbike, now I have the licenceI can go out at nights, my parents allow me to.

• When can means permission the infinitive form is to be allowed to, so I say:When I was young I was not allowed to go out on my ownI will never be allowed to quit my judo classes

Obligation and prohibition• In the affirmative, we use have to and must to

express obligation but only in the present as must doesn’t have a past formI have to do my homeworkI must do the washing-upIn the past I had to do many things in the house

• To express lack of obligation we use the negative form of have to or need toI don’t have to make my bed

• To express prohibition we use mustn’t or may notYou mustn’t touch this switch

Advice

• To express advice we use should or ought to, both in the affirmative and negative forms.You should visit a doctor if you are not feeling wellYou shouldnt have gone to the park today, it’s been raining

all day and you’ll catch a cold• Ought to is less usual than should but we use it in

the same wayYou ought to have told me about it before, I didn’t know

he was illHe oughtn’t to go out at night so often, he’s going to get ill

Deduction and certainty

• We use must to express deduction in the affirmativeLook at his golden watch, he must be very rich

• And we use can’t in the negativeHe can’t be very kind, look at the expression in his eyes

• When we are not so sure we can use may or might• He may be a doctor, he seems to be in charge• She might be an actress, she’s really good-looking

Possibility or probability

• We use may and might to express possibility.• When we are one hundred per cent

something will happen we use willTomorrow it will rain

• When we are not so sure, we sayTomorrow it may rain

• And when it’s even less likelyIt might rain tomorrow