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Concourse 2

Semi-modal verbs and Semi-auxiliary verbs

Semi-modal verbs


There is a general guide to modal verbs and a guide to pure modals on this site.  This section focuses only on semi-modals and what are called marginal modals.

In the following you will find reference to dynamic, deontic, alethic and epistemic modality.  If the terms are unfamiliar, you can safely ignore them but there is a link at the end to a guide in which they are explained.

There is a certain amount of disagreement about what constitutes a semi-modal.  For the purposes of this guide, we are considering verbs which can act both as modals and as 'ordinary' lexical verbs.



Dare is an ancient word with connections to words pre-dating Old English.  Nowadays it means something like 'to have the courage to'.  Consider these examples:

Modal verb Lexical verb
  1. She daren't phone her mother
  2. She dared not phone her mother
  3. Dare she phone her mother?
  4. She wouldn't dare phone her mother
  5. I wonder if she dare phone her mother
  1. She doesn't dare (to) phone her mother
  2. She didn't dare (to) phone her mother
  3. Does she dare (to) phone her mother?
  4. She wouldn't dare (to) phone her mother
  5. I wonder if she dares (to) phone her mother

The contention here is that all these sentences are correct grammatically.  What conclusions can you draw?
Think for a little while and then click here.

To many, the modal forms of the verb sound slightly stilted and old fashioned and the non-modal, lexical forms are, in fact, more common as corpus research has shown.  The non-modal forms are also more common in American English.

In most cases, the verb expresses dynamic modality because it refers to the subject rather than to obligation imposed or likelihood imagined.  Other forms of modality occur in the three common set phrases with dare:

  • I daresay he will come later
    This is written as one word and is only used in the first person singular.  It means something like I believe.  Note that this is the only common use of the verb with an assertive sense.  It refers to epistemic modality in that it expresses the speaker's view of likelihood.
  • How dare you!
    This is an expression of outrage and can refer to deontic modality in that it expresses the speaker's view that something is forbidden.
  • You dare! / Don't you dare!
    This is used as a threat of retribution or punishment if somebody does something.

There is a transitive use of dare to mean challenge in expressions such as
    I dare you to jump
    He dared me to do it
    Did he dare you to do it?
etc.  In this use the verb is always a lexical verb, never modal.
Another, even rarer transitive use of the verb occurs in expressions such as:
    She dared the water
    I dared a question

and, again, the verb is always lexical in these meanings.



Need is the only semi-modal which fits into the notions of possibility, necessity etc. along with the true modal verbs.
It does, however, have two non-modal, lexical uses.  Consider these examples:

Modal verb Lexical verb 1 Lexical verb 2
  1. She needn't phone her mother
  2. Need she phone her mother?
  3. Needn't she phone her mother?
  1. She needs to phone her mother
  2. She doesn't need to phone her mother
  3. Does she need to phone her mother?
  4. Doesn't she need to phone her mother?
  1. I need a drink
  2. I don't need anything else
  3. Do you need anything?

What conclusions can you draw?
Think for a little while and then click here.

There is fruitful ground for confusion here, not least in the distinction between She needn't have phoned her mother (but did) and She didn't need to phone her mother (so didn't).

A further source of confusion is that the verb is usually used to refer to obligation, i.e., deontic modality, but it can be used to refer to logical necessity, i.e., alethic modality, as in, for example:
    A rectangle needs to have four sides
and in this case, it is always formed as a lexical verb.
The negative is formed with can't, as in:
    A square can't have more than four sides

Again, to many, the modal form, especially the question, sounds formal and slightly stilted and again, the form is rarer in American English.

used to

used to

The verb is used to talk about

  • things we did in the past but no longer do (I used to live in Manchester)
  • habits we have discontinued (I used to eat chocolate when I watched TV)
  • states that no longer exist (People used to be more friendly).

There used to be (!) two forms with identical meanings, thus:

Modal verb Lexical verb
  1. She used to live in Margate
  2. Used she to live in Margate?
  3. She usedn't to live in Margate
  4. Usedn't she to live in Margate?
  1. She used to live in Margate
  2. Did she use(d) to live in Margate?
  3. She didn't use(d) to live in Margate
  4. Didn't she use(d) to live in Margate?


  1. The modal forms are still encountered and should (perhaps) be taught for recognition purposes but the non-modal, lexical verb is now more common and, it seems fair to presume, will continue to grow in popularity.
    To many, the modal form is formal, stilted and even wrong.
  2. There is no requirement only to use the modal in non-assertive contexts.  This is unlike need and dare (see above).
  3. There is some spelling confusing.  The 'd' is optional where shown in brackets, compulsory otherwise.
  4. Confusion with the be/get used to structures (as in, e.g., I'm used to working late) can mostly be avoided if you don't present them in the same lesson.
  5. The pronunciation of this verb to express habit varies from the verb meaning to employ: the 's' is pronounced /s/ in the former and /z/ in the latter.
  6. Used to can be replaced by would usually after used to has set the scene.  For example, We used to take our holidays in Margate where we would stay in a guesthouse and would go swimming every day ... .
    However, only used to may refer to past states (He used to be so slim not *He would be so slim).

half moon

Semi-auxiliaries or Marginal modals

Apart from pure and semi modal verbs, there is a class of multi-word verbs which are often referred to as semi-auxiliaries (and just as often dumped into the semi-modal category).  They are also called marginal modal verbs because they are often lexical equivalents of true modal verbs.
What you call them is of little consequence but their behaviour requires special treatment in the classroom because they, too, act like modals insofar as they:

  • express the writer / speaker's view of reality
  • occur in combination with main verbs and in some senses cannot stand alone

They all, however, make questions and negatives as main verbs do and cannot be inverted for questions or negated without an auxiliary (do).

A short list includes:

happen to
As in, e.g.,
    I happened to see John yesterday.
The sense is
    By chance I saw John
rather than by arrangement or plan.
care to
This is similar in sense to would like to but can only be used non-assertively so we can have:
    Do you care to go out?
    I don't care to eat in smoky restaurants

but not
    *I care to eat out
mean to
This semi-auxiliary is often used for intentions in the same way that going to is used as in, e.g.,
    I mean to call on him on my way.
seem to
This verb has no modal equivalent and is often classified (wrongly) as a copula.  It is a copular verb when it is used without another verb as in, for example:
    He seems happy
The sense of seem to is different and is usually one of doubt or uncertainty so it belongs with the pure modals such as might, may, could etc. as in, e.g.,
    He seems to be unhappy
It expresses epistemic modality because it concerns the speaker's view of the likelihood of a proposition being true.
tend to
In the present tense this verb suggests preference (and, therefore, habit) as in, e.g.,
    I tend only to watch the news on TV.
In the past, however, it often performs the same function as the semi-modal used to as in, e.g.,
    We tended to take long walks on our holidays
    We used to take long walks on our holidays.
turn out to
This is often not classified as a semi-auxiliary (and it is not one in something like The weather turned out nice).  However, it has affinities with auxiliaries in expressions such as
    He turned out to want even more money
This verb also has a copular use in, for example:
    The weather turned out nice.
be about to
This semi-auxiliary is also often used as an equivalent to going to but emphasises the close proximity of the events in time.
Both are used in the past to refer to a frustrated plan.
Compare, e.g.,
    I was about to have dinner when you called
    I was going to have dinner when you called.
Both are used in the present to refer to a future based on current evidence or previous experience (and so are epistemic in sense).  E.g.
    Look at the weather.  It's about to rain / It's going to rain
    Don't argue any more; she's about to / going to lose her temper.
be likely to
This is modal in nature and clearly expresses a degree of probability so belongs with pure modals like may, could, will etc. and concerns epistemic modality.  Compare, e.g.,
    He's likely to be late
    He may well be late
be supposed to
This has affinities with modals such as should, ought to and must (in some senses) and refers to obligation (deontic modality) and to likelihood (epistemic modality).
Compare, for example,
    You aren't supposed to be in here
which is deontic, with
    You shouldn't be in here
    The train ought to be here at 6
which is epistemic, with
    The train is supposed to be here at 6.
There is sometimes a sense with this construction that the event or state has not taken / will not take place although it should.  Compare, e.g.:
    He's supposed to be here already (but he isn't)
    He should be here already (and I think he is)
    I should go (and probably will)
    I'm supposed to go (but probably won't)

teaching semi-auxiliaries

If the teaching of modality starts (as it very arguably should) with meaning and speaker perception, then integrating the semi-auxiliaries into lessons focused on notions such as probability, permission, prohibition, futurity, intention and so on is quite straightforward.
The forms are easy enough to teach and the usefulness of the verbs is often overlooked, especially as some have no clear modal-verb equivalents but still refer to the speaker's perception of events and states.



This verb is somewhat anomalous, quirky, even, and many analyses will not consider it a modal verb of any type.  Here it follows the section on marginal modals but could just as easily be inserted after the semi-modal verbs proper.  It shares some modal characteristics as well as functioning as a causative or main verb in, e.g.:
    I let my students leave early (causative)
    They didn't let me finish
    Do they let dogs in here?
(main, transitive verb)
There is a guide to the causative on this site.

When it takes on its modal clothes, the verb is used to oblige, make suggestions and make offers (deontic modality again) and it works like this:

Offer / Obligation / Permission Suggestion
  1. Let me help you
  2. Let him help
  3. Did she let you help?
  4. Did they let you come in?
  5. She doesn't let me help
  6. The boss lets me go early
  1. Let's go to Margate
  2. Let's not go to Margate
  3. Don't let's go to Margate

In the functions of offering, permission and obligation, the verb has no modal characteristics (it has a past form [irregular and unchanged], takes a third-person -s and forms questions and negatives with the do operator).  The form is usually one of a simple imperative and can be softened with please etc.

The verb works as a modal auxiliary, however, insofar as it cannot appear without a main verb and implies suggestion, obligation and so on.

  • It is almost always abbreviated to let's rather than keeping the full form which is reserved for a persuading / obligation function.
    Compare, for example:
    • Let us try harder
      which, depending on setting and participants, could be an obligation equivalent to:
      We must try harder
      or it could be a rather formal suggestion.
    • Let's try harder
      which is simply a suggestion more or less equivalent to
      We should try harder, shouldn't we?
  • When the verb is being used as a main verb in the imperative with a meaning connected to allow, there can be no contraction so:
        Let us free
    cannot be contracted to
        *Let's free
  • As a response to a suggestion using shall such as:
        Shall we go now?
    the use of:
        Yes, let's
    is common as a way of acceding to a suggestion.
  • Suasion: there is a rare and somewhat formal, if not poetic, use of let with a main verb in the subjunctive in expressions such as:
        Let it rain
        Let the sun shine
        Let him be promoted

    The use here is called optative (wishing).
    There is a further unusual use as a kind of challenge in, e.g.:
        Let him try!
        Let them come!
  • Negatives:
    • There are two negative forms, the second of which is informal at best:
      Using not in the same way that pure modals make negatives as in, e.g.:
          Let's not tell him the truth
      Using the do operator as in, e.g.:
          Don't let's tell him the truth
    • The verb cannot be used in the positive (i.e., assertive form) as a suggestion-making device in the second person so
          *Let you give me a hand
      is not allowed.
      but there is a purely negative second-person use with the operator do as in, e.g.:
          Don't let anyone tell you it will be easy
    • The optative use in e.g.
          Let it snow
      can be made negative with the insertion of not before the main verb in e.g.:
          Let him not come too early
          Let the snow not get too heavy
      Although some might think it wrong, there is also a negative using the do operator:
          Just don't let it rain
          Please don't let him get the job
      As in the examples, these are often prefaced with just or please.
      The challenge use mentioned above in, e.g.:
          Let him do his worst!
      cannot be negated.
  • Interrogatives:
    • There is no pure interrogative form for the modal use so
          *Let we go?
      is not permitted.
    • There is a question-tag formula which betrays the modal nature of the verb as in, e.g.:
          Let's go, shall we?
      and that's roughly equivalent to
          Shall we go?
      and that cannot have a tag so
          We shall go, shan't we?
      carries only future reference, not the idea of suggestion.

(Incomplete) Summary


Related guides
the essentials of modality a simpler guide in the initial training section
pure modals taking each pure modal in turn and identifying its function
modality: tense and aspect which considers modal verbs and perfect and progressive forms
complex tenses which also considers complex tenses in relation to modality
teaching modality for some more ideas transferable to the analysis above
types of modality for more on types of modality such as epistemic and deontic modality
copular verbs for a little more on how seem and turn out can be used
assertion and non-assertion for a little more on the differences between these ideas