Unit 8: modality

impossible

Modality refers not to how we see time or how we see the meaning of words but to how we perceive events in terms of their:

likelihood (technically, epistemic modality)
As in, e.g.:
That must be her brother
She can't have arrived yet
permissibility (technically, deontic modality)
As in, e.g.:
You can go now
You mustn't say such things
ability and willingness (technically, dynamic modality)
As in, e.g.:
I couldn't help laughing
Will you help me, please?

This can be a very technical area but we are going to deal with it in two sections only and leave you to do more research by following some of the links.
The technical terms used above, epistemic, deontic and dynamic, may look a bit scary but they are useful.
The two areas are:

Section	Looking at:
A	Modal auxiliary verbs The verbs we use to make modal statements.
B	Other forms of modality Other forms of the language which function similarly.

As usual, clicking on the yellow arrow at the end of any section will return you to this menu.

Section A: Modal auxiliary verbs

The verbs

The usual list of modal auxiliary verbs in English includes these:

Pure or central modal auxiliary verbs

Semi-modal auxiliary verbs

used to | need | dare

We'll look at the first set of ten pure or central verbs first and then consider the others.

What is special about these 10 verbs?

We have seen, in Units 6 and 7 of this course (and elsewhere) that main verbs generally behave quite predictably so they:

They carry meaning when they stand alone as in:
    Go!
    I hope
    We accept
etc.
Form questions and negatives in the simple past and present with the verb do as in
    Do you like this?
    Does she want to come?
    Did you get the money?
    I don't love him
    She didn't have time
    It doesn't work
etc.
They can occur together as in
I came to help prepare the room
I remember asking about that
They inflect, regularly or not, for the past tense as in:
arrive-arrived, come-came, buy-bought, work-worked
etc.
They take an -s or -es in the present simple tense when used with the third-person singular as in:
I smoke-she smokes, we ask-he asks, they carry-Mary carries, you pass-it passes
etc.
They can take a progressive aspect by using be + -ing as in:
She is smiling
They are playing

Modal auxiliary verbs are very different and do none of these things:

They do not carry a meaning unless they are paired with a main verb so, for example:
    She can
    We must
    Should
are all meaningless without a very clear context or the addition of a main verb.
They form questions by swapping around the subject and the verb and negatives by just adding n't or not to the verb as in:
    Can you?
    We can't
    They mustn't
    Should I?
    Couldn't you?
    Won't I?
etc.
They cannot occur together in standard English so we do not see:
    *I can must
    *She could should
    *They ought might
etc.
They do not carry inflexions for the past tense (although some have past forms using different verbs) so we cannot allow:
    *She musted
    *They canned
    *I mighted
etc.
There is no -s or -es inflexion on the third-person singular form so we do not see:
    *She musts
    *It cans
    *He shoulds
etc.
They do not occur with a progressive form using be + -ing so we do not see:
    *I am musting
    *They were canning
    *He is shoulding
etc.

You can take a quick test to check you have all this by clicking here.

The missing parts

Most modal auxiliary verbs do not have past tenses at all and some do not allow a future form so English uses a substitute form. There is no past or future of must for example, so English uses the verb have to as a substitute.
Equally, the verb can has no past in some meanings and no future so be able to is substituted.

Here's a short list of the forms:

Present	Past	Future
can go	could go was able to go could have gone	will be able to go
could go	could have gone	could go
may go	could go may have gone	may go
might go	might have gone	might go
will go	would go	will go
must go	had to go	will have to go
should go	should have gone	should go
ought to	ought to have gone	ought to go

To make matters more difficult still for learners, the meanings often alter depending on the tense.

As you can see, for many of these verbs, the present form serves also for the future so we can say, for example:
You may go
which expresses permission in the present but when it refers to the future, it usually expresses likelihood as in
I may go to the party on Saturday

What about the semi-modal auxiliary verbs?

The semi-modal verbs sometimes have the characteristics of the central modal auxiliary verbs and sometimes they work just like main verbs when we make negatives and questions so, for example, we can have

Central-like	Main verb-like
I usedn't to like olives	Did she used to live here?
I needn't go	I don't need to go
I daren't ask	She didn't dare go

They perform similar functions in the language, expressing the same ideas as the central modal auxiliary verbs (barring the verb dare which carries the unique meaning of have the courage or temerity to do something).
There is a guide to them, linked below, which explains their complexity at some length.
They are difficult.

What do the verbs do?

As was said at the outset all modal auxiliary verbs express the speaker / writer's view of likelihood, permissibility, willingness or ability.
Unfortunately, there is no one-to-one relationship between the verbs and what they mean. For example, the verb could often refers to

personal or dynamic modality: ability and willingness: I could swim well as a child
She could help me because she understands the program
Could she speak good Greek?
It was so heavy, two of us couldn't lift it
I could do that for you
Could you help me with this, please?
likelihood or epistemic modality: That could be our bus
I could have left my keys at work, I suppose
That couldn't be the only reason
Could he be her brother, do you think?
permissibility or deontic modality: Could I ask a question?
You could have left at any time
We could leave early on the last day

and all the other modal auxiliary verbs are similarly multi-functional.

There are guides on this site to all forms of modality and the place to start is the link to the map of modality and the essential guide to the area, both linked below.
However, very briefly, these are the main areas of modality in which the verbs operate with some examples:

Area	including	Verbs and examples
personal (i.e., dynamic)	ability willingness	I can't speak French I can help you Will you marry me? Could you wait a little? I would love to come Are you able to stay?
likelihood (i.e., epistemic)	possibility impossibility deduction conclusion speculation	That can't be right It could explode The figure ought to be higher This should be the right answer I may be able to help He should have arrived by now if he left on time That must be her brother She might feel better in the morning
permissibility (i.e., deontic)	obligation non-obligation permission prohibition necessity non-necessity advice	You must buy a ticket before you get on the train You needn't explain May I leave? Could I interrupt? You can't park here You need to take ID with you You don't have to come She should get to a doctor She ought to work harder

As you can see, lots of verbs operate across the spectrum of modal meanings and the list above is not complete.

Learn more

If you want to discover more now about modality and modal auxiliary verbs, go to:
the essential guide to modality
which has links to other guides.
If you are concerned to investigate the whole area, try:
the modality map

Take a test

Try a test which focuses on the meanings of some common modal auxiliary verbs.

Section B: other modal forms

It's definitely level

Very often, the discussion modality stops at a summary of the main modal auxiliary verbs (both central and semi-modal sometimes).
There are, however, many other ways that English and all languages have of expressing the same concepts signalled by the verbs.

Here's a list with some common examples of the forms and their modal auxiliary verb equivalents.

Verbs	Equivalents	Adjectives	Equivalents	Adverbs	Equivalents
likelihood:
That proves it's true The light shows the power is on I doubt if that's true	It must be true The power has to be on That may not be true	That's certain to be the case It's evident he's lost It's obvious she's not coming	That must be the case he may well be lost She can't be coming	That certainly possible It's clearly not working That's definitely not him	That may be possible It can't be working It couldn't be him
permissibility
I allowed them the time I am instructing him to do it Am I obliged to take a test?	They could have the time He must do it Do I need to take a test?	Is this compulsory? It an essential part It is necessary to pay for it	Must I do this? This part has to be here Do we need to pay?	You were needlessly rude It was pointlessly broken That was unnecessarily long	You didn't have to be rude It shouldn't have been broken That ought to have been shorter
ability and willingness (there are fewer of these because modal auxiliary verbs are preferred in English)
She didn't manage to go I'm offering to help	She couldn't go I'll help	I was stumped for an answer I was successful	I couldn't answer I could do it	He did it poorly That was ably done	He couldn't do it well He was able to do it well

There is also a range of modal nouns which are frequently used to express levels of modality and they include, for example:
For likelihood:
    certainty, belief, suspicion
etc.
For permissibility:
    compulsion, necessity, obligation, suggestion, advice
etc.
For willingness and ability:
    offer, ability, achievement, success
etc.

Learn more

There is one guide on this site to modality without modal auxiliary verbs at:
modality without modal auxiliary verbs

Take a test

Try a test of your knowledge of the whole of this guide.
Use the 'Back' button to return when you have done that.