Modal Verbs

Modal verbs (defective verbs) - Common characteristics They have not all verb forms. They do not take s in the 3rd person of the present tense singular. (e.g. he can) They form their interrogative forms by inversion. (e.g. May they.... ?) They form their negative forms by adding not (e.g. must not, cannot!) All these verbs are followed by bare infinitive except the verb ought)

Which modal verb to use? Ability or potential: can, could, be able to Possibility and permission: can, could, may, might Requests and suggestions: might Expectation or probability: should, ought to Inference in logical conclusion: must, can’t Prediction: shall, will Advice and recommendation: shall, should, ought, had better Obligation and necessity: must, musn’t, have to Absence of obligation and necessity: needn’t, not need, not have to

May & Might May – for present and future Might – for past and conditional Negative forms: may not (mayn’t), might not (mightn’t) *Might is less certain than may or could. May is used for permission and possibility.

May – for permission e.g. I may go. To make past we use allow (not might) e.g. I may go today. I was allowed to go yesterday. Formal permission is always expressed by may. e.g. May I use your phone? (is more polite than can/could I...)

May – for possibility May/might +present infinitive = possibility in the present or future. e.g. He may come today/tomorrow. She might not know the answer. (Perhaps she doesn’t know.) Might must be used when the main verb is in the past. e.g. He said that he might be late.

May/Might Might/May in interrogative is not used. Instead: Do you think + present or future tense or Is he likely + an infinitive

May/Might May/Might + perfect infinitive = for past e.g. He may/might have gone. = It is possible that he went. Third type conditional sentences. e.g. If we had taken the other road we might have arrived earlier. Instead of will/would to indicate a possible instead of a certain result. e.g. If he sees you. He will/might stop.

May/Might With future time reference we can use may / might / could + PRESENT PARTICIPLE and PAST PARTICIPLE to say it is possible that something will happen in the future: e.g. Ray’s flight was cancelled, so he may/might/could be arriving much later than expected. e.g. The thieves may / might /could have left the country by the time we get to the airport.

May/Might May/Might in casual commands e.g. You might post this for me. = Post this for me, will you. (between friends) May + infinitive for hope and faith e.g. May you be happy. (= I hope you will be happy.)