Chapitre 4: Defective (modals) - Anglais Troisième | DigiClass
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Defective (modals)


Defectives are also known as modals, they are auxiliaries such can, may/might, ought to, should, will, would.

They don’t have the infinitive form and do not take S at the third person singular; also they do not have all the tenses.


Can is used to express:

  1. Capacity→ $\textbf{Eg:}$ Can you help me pound my millet?

Can is used with verbs of perception:
$\textbf{Eg:}$ I can hear him crying deeply

  1. Possibility→ $\textbf{Eg:}$ Travelling with this bush taxi can be dangerous.
  2. Permission → It is used with the usual form of expressing permission with a first subject;

$\textbf{Eg:}$ I can use this motorcycle if I want; with other person,it express a less formal or less polite request.

$\textbf{Eg:}$ Can we go to the movies?

Could is the past or conditional (subjunctive) of CAN;It is used to express a past possibility or ability. The equivalent of CAN is: To be able to.

NB : Negative form : cannot / can't


Must serves to express obligation or command.

     Eg:You must stop dating girls at random.

It is also used to express a recommendation or a strong advice.

     Eg: One must not urinate here

NB:There is no past form of must; for that, we use the equivalent.

The equivalents of must are:

  1. To be obliged to
  2. To have to

Negative form : Must not / mustn't


It expresses possibility or probability either in the presenter future time.
       Eg: It may rain tonight

May is appropriate for expresses permission ; it is more polite than CAN.

       Eg: May I go out, please?

May is appropriate for expressing wishes.

       Eg: May God hear you!

In the negative, may not/might not expresses an improbable action.

       Eg: Mother must not come to the wedding ,he got a visit.

May not can also express a formal refusal of permission.

       Eg: May I get in? Not,you!   No, you may not.

Might is used alternatively with may to express present or future possibility or probability but might increases the doubt and seems to be more current.

NB : Negative form : May not

       Eg: He may not fail his exam.

V.  Future of Can, Must, May

To get their future we use shall/will with their  equivalent expressions.

Rule : S + shall/will + equivalent expression + Infinitive of verb + C

Eg : - I can speak French I shall be able to speak French

       - Can she cook well ?   Will she be able to cook well ?

       - I must stay here   I shall have to stay here

       - We may do this   We shall be permitted to do this.

       - May he go out   will he be allowed to go out.


VI.  Preterit / Past simple of Can, Must, May

  • Can

The preterit of Can is could.

Eg : - I can carry a bag  I could carry a bag

       - Can you hep him ? Could you help him ?

       - We cannot /can't see the sea We could no / couldn't see the sea

  • Must

We use have to in the preterit : had to

Eg : - He must speak Moore He had to speak Moore

        - Must I play alone ?  Had I to play alone ?

        - Boys must not be inside. Boys had not to be inside.

  • May

We use be permetted to / be allowed to int the preterit : was/were permitted to or was/were allowed to.

Eg : I may talk I was permitted to talk

       - May they sing ? Were they allowed to sing ?

NB : Might is often considered as the past of may mainly in reported speeches.

VII.  Present perfect of Can, Must, May

  • Can

We use be able to in the past participle with auxiliaires have/has + been able to

Eg : - I can copy this text  I have been able to copy this text.

        - I can see the tree I have been able to see the tree

       - can she cook ? Has she been able to cook ?

       - we can't fly We have not been able to fly.

  • Must

We use have to in the past participle (had to) with the auxiliaires have/has.

Eg : - He must travel He has had to travel

        - Must girls stay here ? Have girls had to stay here ?

  • May

We use be permitted to / be allowed to  in the past participle ( benn permitted to/ been allowed to) with have/has.

Eg : I may follow him I have been permitted to follow him

       - May he burn papres?  Has he been allowed to burn papres ?