Modal verbs

Modal verbs

A short summary

Table of content

Basic rules

Can

Can't

Could

May and might

May not

Difference between may and might

Should

Must

Mustn't

Difference between must and have to

Difference between mustn't and don't have to

Modal verbs in the past

Basic rules

− They usually don’t stay “alone” in the sentences. − In basic forms they are followed by a verb in infinitive in order to express present or future activities.

Can

1. Permission−to ask for or give permission or to request something You can use my umbrella, I don't need it right now. Can I sit in that chair please? 2. Ability −to be (physically) able to do something − to know how to do something. Birds can fly. Elephants can't fly.

3. Possibility − to a theoretical possibility − important that we don't use can to talk about future possibilities. For this you would use may or might. It can get cold there at night so take a jacket. I know you can win the competition.

Can't

1. Prohibition− used when something is forbidden or not allowed We cannot park the car next to this fire hydrant. You can't drive as fast as you want in the city. There are speed limits.

2. Uncertainty − used when you are sure that something isn't true or something is surprising It can't be dark outside! It's only 4.30pm! They can't have landed on the moon, I'm sure it's a hoax.

Could

1. Ability in the past− used to express ability in the past I could ride a horse when I was younger but now I can't. 2. Politeness − used to ask for permission or to request something Could I please use your bathroom? 3. Permission in the past In high school, we couldn't leave the classroom without a pass.

4. Certainty − used when you are sure that something is untrue That couldn't be my cat meowing outside, it was hit by a car last week. 5. Suggestion He could try and fix it himself. We could go to the movies if you are interested.

May and might

3. Asking for permission− important that can is used more frequently than may in spoken English though may sounds more polite May I sit next to you? May I borrow your pen? 2. Permission You may leave the table once you have finished your meal. You may take only one brochure.

1. (Future) possibility − a chance that something is true or that there is a possibility of something happening − important that might is used more frequently than may in spoken English. It might rain later. (It is possible that it will rain.) I might go to the movies tonight. (Though I'm not sure.) I wouldn't talk to Tim right now. He may still be angry after his team lost.

May not

− can be used to NOT give permission or to prohibit someone from doing something You may not park your car in front of the gate. You may not take more than one brochure.

Difference between may and might

− can normally be interchanged without significant difference − might often implies a smaller chance to something happening. It may rain. (70%) It might rain. (40%)

Should

3. Likelihood int he present int he future - prediction They should win the game because they are a much better team. 4. Obligation – not so strict, polite − sometimes should is used instead of must to make rules, orders or instructions sound more polite Passengers should check in at least 2 hours before departure time. You should never lie to your doctor.

1. Advice and suggestion − to say that it is the right thing to do or the correct thing Does your tooth still hurt? You should make an appointment with the dentist. I think you should study for the test so that you don't fail. 2. Likelihood int he present Mary should be at home by now. Give her a call. He should have the letter by now. I sent it a couple of weeks ago.

Must

3. Deduction − used when we don't know, but we are certain that it is true based on evidence Look at all of that snow. It must be really cold outside. The ground was wet this morning. It must have rained last night. 4. Strong recommendation − something that is highly recommended (stronger than using should) We really must get together for dinner sometime. You must see the new Peter Jackson movie, it's fantastic.

1. Obligation, duty − refers to laws and regulations. I must memorize all of these rules about modal verbs People must remain seated until the show is over. 2. Necessity Humans must drink water at least every two days. You must give up smoking, it's bad for you.

Mustn't

−refers to prohibition (negative obligation) You mustn't use your smartphone while you are driving. You mustn't get on the subway if you haven't paid for the ride.

Differences between must and have to

− Must can be replaced by have to with little difference in meaning You have to study. (You must study.) He has to finish the report by Friday. (He must finish the report by Friday.) − Have to is a more informal while must is mostly used in written orders or instructions − Must expresses obligation imposed by the speaker while have to expresses external obligation Teacher: You must complete this essay by Friday Student: We have to complete this essay by Friday.

− When we are mentioning someone else's obligations, we use have to. John has to quit smoking. − For questions it is more common to use have to instead of must (which sounds very formal) When do you have to pay finish the report? Does he have to take a blood test? − The past tense of must is had to I had to pay my speeding ticket yesterday.

Differences between mustn't and don’t have to

You must not drink that. (It is forbidden to drink that; it is not allowed.) You don't have to drink that. (You don't need to drink that but you can if you want.) You mustn't tell John (Do not tell John.) You don't have to tell John (You can tell John if you want to but it is not necessary.)

− mustn't is a negative obligation − important that you do NOT do something while don't have to is an absence of obligation. − mustn't = it is prohibited; it is not allowed − don't have to = no obligation; you are not required to do something, especially if you don't want to.

Modal verbs in the past

− Form: modal verb + have + V3 That must have been my mother calling me last night, nobody else has my number. She is late. I think she may have missed her plane. We were lucky because it could have rained but it didn't. She could have married anyone she wanted to. You should have given your boss the report yesterday when he asked for it.

Modal verbs in the past

− Form: modal verb + have + V3 That must have been my mother calling me last night, nobody else has my number. She is late. I think she may have missed her plane. We were lucky because it could have rained but it didn't. She could have married anyone she wanted to. You should have given your boss the report yesterday when he asked for it.