CAN, COULD, BE ABLE TO
The modal verbs can and could are often used with perception verbs. Sentences such as I can hear you, he could
smell the smoke, etc., are much more frequent than expressions I hear you or he smelled the smoke.
The verbs which occur with can/could:
|hear||Can you hear that sound?
Don’t shout. I can hear you perfectly well
|see||Can you see that man on a bike?
I can’t see anything. It’s dark here.
|remember||I can remember my first day at school.
I couldn’t remember the title of the book.
|feel||I can feel it in my bones.
Can you feel the heat?
|smell||I can smell something strange.
Could you smell gas?
|understand||I can understand why you don’t want to go.
I couldn’t understand a word she said.
The modal verbs can and could have very limited usage. These cannot be used in perfect tenses, have no future form or infinitive, etc.
In such situations, these verbs are replaced by the structure be able to.
It takes place:
- after another modal verb
You can find her either in her office or at home.
You should be able to find her either in her office or at home.
- in tenses other than Simple Present (can) and Simple Past (could)
I have never been able to learn Japanese, although I’ve tired.
Will you be able to help me with all the housework?
- in structures requiring the usage of an infinitive or gerund form
It’s very nice to be able to meet your friends.
She was grateful for being able to be with us.
- when we describe what a person may/may not have done in a given situation in the past
I could speak English pretty well, but I wasn’t able to utter a word during my exam.
MUST, HAVE TO
Both the modal verb must and the ordinary have to express the obligation, but their usage is different.
A necessity resulting from the belief of the speaker is expressed with the verb must.
You must come to my party.
I must buy a new record.
A necessity resulting from someone else’s order, command or regulation is expressed by the verb have to.
I have to be at work before 8 o’clock.
You have to wear a seat belt in a car.
A necessity resulting from the so-called “higher power” is also expressed with the verb have to.
She has to go to the hospital.
We have to find another hotel.
In everyday speech, we are more likely to use the short form have got.
It’s getting late. I‘ve got to go.
We‘ve got to come to work on Sunday.
The verb must, like majority of the other modal verbs, has only one form. It can only be used to describe the present and the near future.
In the other tenses, instead of must, we should use have to, which is subject to the same rules as English verbs.
|present||We must go.|
|past||We had to go.|
|future||We’ll have to go.|
In such a situation, it does not matter whether the verb describes an internal obligation or a necessity resulting from external circumstances.
The verb “have to” forms questions and negative forms in a typical pattern – with the auxiliary verbs or the inversion.
What time does he have to leave?
Do you have to give the book back today?
Did you have to call the police?
MUSTN’T, NEEDN’T, DON’T NEED
If we would like to express the lack of obligation or necessity, we choose one of the two following constructions:
- not have to
I don’t have to be at home before midnight.
- not need to
I needn’t be/ don’t need to be at home before midnight.
We form the negative sentence in two ways: needn’t to or don’t need to.
Both constructions can be used interchangeably.
The negative form of must is mustn’t, but its meaning is completely different! Mustn’t express a prohibition.
You mustn’t park here!
The modal verbs may and might have a similar meaning. The verb may is used to express requests and asking for permission, but it is more official and polite than the verbs can and could used in similar circumstances.
Can I sit here?
Could I sit here?
May I sit here?
The verb “may” can also express permission.
You can take my car.
You may take my car.
The verbs may and might are used to define possibilities, to describe what is possible.
Lucy may/ might know his mobile number.
The alternative to may and might is could.
Lucy could know his mobile number.
We create a negative form by adding not to the verbs may and might, using full forms:
might/might not, may/may not.
SHOULD, OUGHT TO
Besides, the verb should describe above, advice, suggestions, and recommendations can also be expressed with the verb ought to. The meaning of both phrases is similar. The only difference is that after ought the main verb appears in an infinitive with to, hence the expression is written as ought to.
We should buy more food = We ought to buy more food.
Ought to form questions and negative sentences in the same way as other modal verbs.
Ought I to write him?
You oughtn’t to worry.
Despite the same usage, ought to occur less frequently than should, perhaps due to the pronunciation and the formation of clusters of consonants, e.g. negative form oughtn’t to.