Verbs: Modal verbs

Modal auxiliary verbs (or modals for short), as the name suggests, are a kind of auxiliary verb. They have most of the attributes of auxiliary verbs. They are a closed class that is identifiable as a short list, and they convey particular types of meaning.

Here is a table which lists the most important modal verbs (also called the core modals). It shows most of them in pairs as present and past tense forms, which makes them easier to remember.

present tense past tense
  • will
  • would
  • can
  • could
  • may
  • might
  • shall
  • should
  • must
  • n/a
  • ought (to)
  • n/a

When we discuss modal verbs, we often discuss modality and modal meaning. Consider the modal verbs can, will, and must, below.

  • She can go to the hospital.
  • She will go to the hospital.
  • She must go to the hospital.

We can radically change the meaning of the sentence simply by changing the modal verb.

In these sentences the modal verb implies different things.

  • She can go to the hospital.
Possibility
  • She will go to the hospital.
Futurity
  • She must go to the hospital.
Obligation

Modal verbs allows us to express different shades of meaning about statements without being long-winded. Without modals, we would have to use various other means such as maybe, if possible, it is necessary that, etc.

What do the following sentences mean?

  • She can go to the hospital.
  • She may go to the hospital.
  • She could go to the hospital.
  • She might go to the hospital.

Do they mean the same thing?

All of these modal verbs express possibility. However, they have subtly different meanings. One way to think about this is to tell yourself a story. Are there ways of continuing the sentence which make sense with one modal, but not with another?

Suppose we continue the sentence with an explanation.

  • She can go to the hospital because she has a car.
  • ?She may go to the hospital because she has a car.
  • She could go to the hospital because she has a car.
  • ?She might go to the hospital because she has a car.

Here can and could seem to be more ‘natural’ here. May and might have more of the sense of choice, and therefore appear awkward in this context.

Suppose we put in an explanation about the Subject’s choice:

  • ?She can go to the hospital because she is anxious about her health.
  • She may go to the hospital because she is anxious about her health.
  • ?She could go to the hospital because she is anxious about her health.
  • She might go to the hospital because she is anxious about her health.

Which of these sentences seem more natural now? Consider adding choose to after the modal: She can [choose to] go to the hospital. Does this make sense?

As a guideline, can and could are often better for expressing ability, whereas may and might are better for expressing choice.

For example, we might say:

  • We can leave now but we may go later.

Can and may are frequently used interchangeably. Some people think that may is more old-fashioned, but it is a perfectly normal alternative to can, and more naturally expresses choice.

Can/could and may/might are present tense and past tense modal forms. Historically, could simply meant ‘can in the past’. However, this distinction is not so strict in modern English. Consider:

  • He can run a mile in five minutes today.
  • He could run a mile in five minutes today.
  • *He can run a mile in five minutes when he was young.
  • He could run a mile in five minutes when he was young.

This looks more like a strict rule: when talking about the past, use could. But you can also use could to refer to present time.

Here’s the same issue, with may and might.

  • He may [choose to] run a mile in five minutes today.
  • He might [choose to] run a mile in five minutes today.
  • *He may [choose to] run a mile in five minutes when he was young.
  • He might [choose to] run a mile in five minutes when he was young.

Again the present tense can/may seems to express future possibility relative to the present, and so does not sit well in a sentence about the past.

So far we have discussed modal verbs expressing ‘possibility’. Another group are the necessity modals, will, shall, should, and must, and the semi-modals have to, need to and ought to:

  • She will go to the hospital.
  • She shall go to the hospital.
  • She should go to the hospital.
  • She must go to the hospital.
  • She has to go to the hospital.
  • She needs to go to the hospital.
  • She ought to go to the hospital.

Can you identify the meaning in each case? Write down your answers and discuss them in class.

Here are our answers. Did you agree with them?

  • She will go to the hospital.
Futurity
  • She will go to the hospital.
Obligation
  • She is obliged to go to the hospital.
  • She shall go to the hospital.
Futurity
  • She will go to the hospital.
Empowerment
  • She is enabled to go to the hospital.
  • She should go to the hospital.
Recommendation
  • It is recommended that she go to the hospital.
  • She must go to the hospital.
Obligation
  • She is obliged to go to the hospital.

Note that some of them have more than one meaning, as we have seen with can and may.

Have (to) and need (to) are sometimes called semi-modals. Unlike the core modals, they are followed by a to-infinitive. That is, we say I have to go there, but not *I have go there. Compare: I will go there, but not *I will to go there. Here are some interpretations of the semi-modals:

  • She has to go to the hospital.
Obligation
  • She is obliged to go to the hospital.
  • She ought to go to the hospital.
Recommendation
  • It is recommended that she go to the hospital.
  • She needs to go to the hospital.
Recommendation
  • It is recommended that she go to the hospital.

As with the possibility modals, the necessity modals can have different shades of meaning.

Can you see a difference between ought (to) and need (to)? Can you think of a sentence where you might use one but not the other? 

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