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MODAL AUXILIARY VERBS What are "modal auxiliary verbs"? The verbs can, could, will, would, should, may, might, must, ought and shall are verbs which 'help' other verbs to express a meaning: it is important to realize that these "modal verbs" have no meaning by themselves. A modal verb such as would has several varying functions; it can be used, for example, to help verbs express ideas about the past, the present and the future. It is therefore wrong to simply believe that "would is the past of will": it is many other things. A few basic grammatical rules applying to modal verbs Modal verbs are NEVER used with other auxiliary verbs such as do, does, did etc. The negative is formed simply by adding "not" after the verb; questions are formed by inversion of the verb and subject: You should not do that. Could you pick me up when I've finished? Modal verbs NEVER change form: you can never add an "-s" or "-ed", for example. Modal verbs are NEVER followed by to, with the exception of ought to. What sort of meanings do modals give to other verbs? The meaning are usually connected with ideas of DOUBT, CERTAINTY, POSSIBILITY and PROBABILITY, OBLIGATION and PERMISSION (or lack of these). You will see that they are not used to talk about things that definitely exist, or events that definitely happened. These meanings are sometimes divided into two groups: DEGREES OF CERTAINTY: certainty; probability; possibility; impossibility OBLIGATION/FREEDOM TO ACT: permission, lack of permission; ability; obligation.

        

He should be here by now. I could swim quite well when I was younger. You mustn't blame yourself for this. You might have discussed it with me first. You can't be serious! Could you open the window please? Must you make so much noise? She had to take her brother along with her. We ought to be going.


Modal auxiliary verb

Primary auxiliary verb(s)

Main verb









have been


the baby

Present Past

can could

may might

will would

shall should

Unlike the auxiliaries be, have, and do, modal auxiliaries 1. do not use inflectional endings (-s, -ed, -ing, -en) 2. cannot function as main verbs.

must -------

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.

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.

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.

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.

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!


The verbs can, could, will, would, should, may, might, must, ought and shall are verbs which 'help' other verbs to express a meaning: it is...

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