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If you check my concept of The Verb Structure Circle, you will find that it does not deal with modality; it focusses on the four basic forms of the English verb and the various combinations possible among them. An additional page deals with modality.

This post relates to a lesson on modality we recently had in one of my groups and is meant to summarize what we discussed there with some additional elaborations.

A few notes beforehand on the circle of the four basic forms.

The idea for a circular arrangement came up when I realized that many people strongly associated verb structures – commonly called tenses – with time (translated into ‘Zeiten’ – don’t do that! ;-), i.e western linear time. This leads to strong associations of all forms with (linear) time, which again obstructs true understanding of their semantics. Especially the aspect forms progressive and perfect cannot be adequately understood with linear time in mind.

A proper understanding of the modal WILL, for instance, suffers from its association with time – future time in this case. Course books often call forms with WILL the ‘will-future’, thereby suggesting that this structure’s main semantics is future time reference. Future time reference is part of its meaning, but calling structures with WILL the ‘will-future’ distracts from other forms more commonly used for activities in the future. (And might also limit the understanding of ‘will’ – one of the most difficult modals to find a general description for.)

To give an example: the progressive structure with BE in the first form is often used to express things that we planned to happen some time in the future:

  • We are going to the cinema this evening;
  • I’m meeting friends tomorrow;
  • She is having an operation next week

Understanding this is additionally obstructed by the name we give the three sentence structures above: simple present continuous. No wonder learners of English believe English verb grammar to be complicated and full of exceptions! But in fact, the English verb system is extremely regular; the fault lies within the terms we use to describe it.

There are many ways to talk about the future, and various aspects to consider when we do. In fact, all constructions consisting of a modal auxiliary + the basic form of a verb have future time reference, but future time reference is not the main meaning we express when using them.

Before I go into more detail, briefly back to our two basic first and second forms (commonly called ‘present ‘ and ‘past’ tense). When we try to describe their core meanings, we can come to the conclusion that they are used to express things we believe to be facts. In the case of the so-called ‘simple present’, things we do regularly, habits and routines, scientific facts, lies etc..

The other two structures, progressive and perfect, are constructed with first or second forms of the auxiliaries BE and HAVE respectively, and (unchanging) participles. They also express factuality, but add additional aspects. The progressive, or –ing form expresses limited duration of an activity; an ongoing process that the speaker conceptualizes as temporary by using the progressive form. The perfect form adds relevance or reference of a past activity (or whatever the verb denotes) to the time of speaking (for more details and examples see: The Verb Structure Circle.)

When we want to express something other than factuality – e.g. uncertainty, future plans, predictions, suggestions, recommendations or advice – we can use one of the various modal auxiliaries, depending on what we want to express. So we might define the function or semantics of modality as changing (or modifying) the factuality of a verb using one of a limited number of modal auxiliaries.

There are eight (or nine if you count ‘shall’) modal auxiliaries:

canCan you help me? Asking someone for help or assistance.  
 We can go get something to eat….  Possible action
couldCould you open the door for me, please  Polite requests
 I couldn’t find the answerability/inability (Notice the difference to expressing a skill. There is semantic overlap, but can/could as modals or can/could as words expressing skill or proficiency are not totally the same.  
mustYou must see that film.  Strong recommendation
 ? I must finish this report by noon, my boss told me.

Here better: I have to finish this report…  
Germans often use must to express what one has to do because of an outside obligation. here we more likely use HAVE TO, not MUST
shouldYou should go to the doctor.  Advice
mightIt might occur….  
It might snow tonight.    
Possibility, not certain
mayYou may go now.Permission given by a person in authority.  
 They may have already left.Similar to might. Also expresses a speculation or guess.  
willI’ll open the window.Offer of action at the time of speaking. Note: It’s almost always in the short form ‘ll.  
 Hopefully, we will be able to finish by tomorrow.Here: Expressing a wish or wishful prediction about a possible future fact.  
 The weather will be fine tomorrow.A prediction or a fact we believe will be true in the future.  
  Will is the most difficult modal to find a general description for. Be skeptical whenever someone does.  
wouldWe would if we could (but we can’t)Hypothetical possibility, less likely or even highly unlikely.  
 I would go to the doctor if I were you.  Form of recommendation
 When I was younger, I would love swimming in the local river  Would as expressing a past regular activity of routine (see more examples below table)
shall (#9)Shall I close the window?   Shall we read the text now?Used mainly in questions with first person pronouns.  

Some time in the past I WOULD do something: this use of would expresses past regular activities or routines; also feelings and states:

And I would think to myself….

In the past, we would always drink beer together.

Like the example above – We would swim in the river as kids – the use of would here expresses an activity or action we used to do in the past, but don’t do anymore – a regular activity or routine we stopped doing some time ago; not so much a habit, there we would use USED TO: I used to smoke. Not anymore.

Modality with past time reference

It might occur…It might have occurred* It might occurred
We could do that.We could have done it. (Implied meaning: but we didn’t)  *We could did
They should not come visit us.They should not have come… (But they did.)*They should came

* not acceptable form of the language

As described above, modal structures contrast with the two basic forms simple ‘present’ and simple past:

 We go out every Friday evening.                  We went out last night.

As modal auxiliaries modify the certainty or factuality of the main verb’s meaning, we cannot use the past tense form of the verb when expressing past time reference. So we use the basic perfect form instead. Note that the structures are very regular.


Semi-modals also change or modify the meaning of the main verb, but slightly differently. It is not so much factuality or uncertainty they add to the meaning, but other aspects like obligation, necessity, wish or desire, courage to do something. The main difference to the modals above, though, is that they have a past tense form.

We have to do that.      We had to do that.

We need to do that.      We needed to do that.

We want to do that.      We wanted to do that.

We dare to do that.       We dared to do that.

We used to do that.   Here we only have a past tense form. The meaning of used to do something has by its very nature only past time reference

I’m not sure what category the two below belong to. They also seem similar as the ones above only that they display different structures. Supposed to is in passive structure, going to in progressive (still have to think about these two).

You are supposed to (do something).   (passive)

We are going to meet tomorrow.  (progressive?)

What is the difference between the sentences below?

We were used to doing something.  versus

                               We used to do something.

I was used to going to work by car before the pandemic.  versus 

                               I used to go to work by car before the pandemic.

I was used to drinking beer with my friends, and then I wasn’t allowed to do it anymore.

  versus                 I used to drink beer, a lot, too much….  I used to smoke. I don’t any more.

All express regular habits. What’s the difference?

Some extra notes:

NEED, HAVE and WANT can also function as main verbs

Need: We needed help.

Have: We have no holidays.

Want: I want an ice-cream.

(HAVE in combination with TO changes its meaning completely and does not seem related to the basic meaning of HAVE any more at all. Need to and want to still retain the basic meanings of need and want.)

Can and could can also express ability or skill as general fact or past fact:

I can play the piano. I could play the violin when I was a child.

In this case, they do not function as modal auxiliaries.

Michael Lewis, 1983 writes about modals and I quote:


From chapter 13 The Group of Modal Auxiliaries

We come now to one of the most complicated problems of the English verb. Large books have been written on modality and even on the more restricted subject of the modal auxiliaries. Palmer, Modality and the English Modals, Longman 197, says of the modals:

There is no doubt that the overall picture of the modals is extremely ”messy” and untidy and that the most the linguist can do is to impose some order, point some regularities, correspondences, parallelism…

This subject is not one that lends itself to any simple explanation.

At the same time, while dismissing the idea of the search for a “basic meaning” which may be attributed to each of the modal auxiliaries, Palmer does suggest that although he does not believe such a basic meaning exists:

(This) must not be taken to imply that we cannot look for a fairly generalized common meaning or a set of closely related meanings for each modal. It is only when precision is demanded or invariance postulated that the notion of a basic meaning becomes unrealistic.

So, we are warned….


I would add that the problem lies not so much in our languages, but in our need for theoretical clarity, testable hypotheses, clear descriptions and generalizations. We do not like uncertainty and have created all kinds of scientific methods and mathematical formulas to limit the amount of uncertainty, sometimes believing we can reach a point of total and all-encompassing truth. I’d rather we just simply accept that no such thing exists (and get rid of school grades).

We are all, especially as native speakers of a language, able to understand, in any given context, and in most cases, what the other person wants to express when using a modal. In general, meaning is flexible and has to be as there are thousands of different contexts and combinations possible, and every one may have a slightly modifying effect on the words and expressions used. We mostly understand each other, though we also sometimes fall victim to misunderstandings – it’s in the nature of communication: we don’t always speak the same language, even if we do. But with a little good will and effort we can fix the problem, our languages allow for that.

For learners of the language it is important to listen how those who ‘own’ it (because they developed it as their own from birth on) use it.  And be aware that theoretical explanations, especially when they are called rules, might not always be totally accurate.

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