Unit 12.1

Modals of Speculation

Modal Verbs


Modals of deduction and speculation are also called modals of probability. We find them when we want to make a guess about something.

Different modals can be used depending on how sure you are about the situation.


The most commonly used modals of speculation are can, could, may and must.

Their structures are:

  • Can/Can’t + infinitive;
  • Could/could not + infinitive;
  • May/may not + infinitive;
  • Might/might not + infinitive;
  • Must + infinitive;
  • Should/should not + infinitive;


  • He can’t go to school because there is a heavy snowfall outside.
  • She couldn’t paint this wall with watercolours.
  • Environmental problems and natural disasters may create problems for people.
  • There might be traffic on the main road because of the festival.
  • Nuclear energy must be harmful for the environment.
  • Thunders and lightnings should make noise.


We use modals of speculation when we talk about a present situation.

We use:

  • Can: to talk about something that happens sometimes, something possible;
  • Could, May/might/: for probabilities and predictions;
  • Must: when we are sure about something;
  • Should: to make guess about something that is likely to happen;


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