Grammar: teaching the modals 'ought to', 'should', 'must' and 'have to'.

Modal verbs present specific problems for both teachers and learners. Quite apart from the numerous difficulties associated with meaning, their use also differs from other verbs in a number of ways, notably:

• Forming the interrogative through inversion rather than the use of the auxiliary verb do (so Can I? rather than Do I can?)
• Forming the negative by adding ‘not’ to the modal verb rather than using the auxiliary verb do (You mustn’t and not You don’t must)
• No –sending in the third person singular
• No consistent past forms in some cases.
• Have to, however, is different, forming interrogatives and negatives using doand having a ‘normal’ past form.

In terms of teaching the modal verbs, the list of verbs in the first question suggests that the distinction between ought to and should and must and have to respectively is the key point, which also suggests that the learners in question have reached a fair degree of proficiency in English.

1) Must and have to

A key distinction between must and have to can be found in the negative forms. Whereas You must go and You have to go can be regarded as broadly the same in terms of meaning, You mustn’t go and You don’t have to go are quite different, the first indicating that going is prohibited in some way, or even dangerous, while the second implies an absence of obligation or need.

Another difference between must and have to in the sense of obligation can be found in the nature of the obligation. It is possible to say I’m sorry. I can’t come to the meeting tomorrow because I have to go to the dentist at 3 o’clock but not I can’t come to the meeting tomorrow because I must go the dentist at 3 o’clock. On the other hand, if you have a really bad toothache, you would probably say I really must go to the dentist, although have to could replace must in this sentence. A generalized distinction would be that must refers to an internal need or obligation while have to is used to refer to an external need or obligation. It is probably true to say, however, that must can generally be replaced by have to but have to often cannot be replaced by must so in terms of teaching, it is probably a good idea to teach have to for obligation because it is nearly always correct whereas must is often inappropriate. Must and must not are useful for official notices and instructions, e.g. You must carry your passport at all times and You must not smoke in the toilets.

2) Should and ought to

Should and ought to are basically the same, although should is much more widely used than ought to. The negative and interrogative forms of ought to are becoming increasingly rare. Both should and ought to are used to talk about obligation and duty and to give advice. One way of getting the meaning of should across to learners is to contrast its meaning with that of must and have to as the degree of obligation is considerably less, e.g. I have to go to the doctor as compared to I should go to the doctor.

It is probably a good idea to practise the above verbs using a generative context, i.e a simple context that can generate lots of examples. In the case of should and shouldn’t, you might ask your learners to think of things they should and should do if they want to improve their English. Answers might include You should read a lot in English, You should learn vocabulary in context, You should talk to English people, You shouldn’t talk Arabic in class and You shouldn’t translate everything. Other simple contexts where you give advice might include how to lose weight, what to do if you have a bad cold, how to give up smoking, how to be successful at an interview and so on.

At higher levels, it is more appropriate to contrast different modal verbs and to concentrate on nuances of meaning. At lower levels it is probably best to concentrate on the main meaning of each modal verb rather than to confuse learners by introducing too many meanings at once. In the case of must, for example, its use for expressing deduction or concluding that something is certain, as in The keys must be on the kitchen table, is a useful one but is arguably confusing for learners at lower levels, particularly as the negative form is can’t and not mustn’t.

Many coursebooks introduce the most important modal verbs first and concentrate on their main meanings initially. Make full use of the way coursebooks present and practise the key modal verbs. You don’t need to reinvent the wheel. Contrasting some of the verbs (e.g. have to and should) can help to consolidate the meaning and giving plenty of relevant practice in generative situations should help your learners to understand and use these verbs correctly.

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