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.
I couldn’t hear anything.
|see||Can you see that man on a bike?|
I can’t see anything. It’s dark here.
I could see the car in the distance.
|remember||I can remember my first day at school.|
I’m afraid I can’t remember that song.
I couldn’t remember the title of the book.
|feel||I can feel it in my bones.|
Can you feel the heat?
I couldn’t feel my hand. It had gone numb.
|smell||I can smell something strange.|
Could you smell gas?
People can’t smell as well as dogs.
|understand||I can understand why you don’t want to go.|
Can you understand what I’m talking about?
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.”
|after another modal verb||You should be able to find her either in her office or at home.|
I might be able to go later.
|in tenses other than Simple Present (can) and Simple Past (could)||I have never been able to learn Japanese, although I’ve tried.|
Will you be able to help me with all the housework?
|in structures requiring the usage of an infinitive or gerund form||It’s 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, although it is possible to use “could” here.||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. The necessity resulting from the belief of the speaker is expressed with the verb must:
You must come to the cinema.
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 the majority of other modal verbs, has only one form, so 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 ordinary 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? When will you have to hand the report in?
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
We form the negative sentence “not need to” in two ways: needn’t to/ don’t need to.
I needn’t be/ don’t need to be at home before midnight.
Both constructions can be used interchangeably. Then what about the verb “must”? The negative form of “must” is “mustn’t”, but its meaning is completely different! “Mustn’t” express a prohibition.
You mustn’t go there.
The modal verbs “may” and “might” have a similar meaning.
The verb “may” is used to express a request and when we ask 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” 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 negative form by adding not to the verbs may and might, using full forms:
might might not
may may not
SHOULD, OUGHT TO
Advice, suggestions, and recommendations can be expressed by the verb “should” or “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 to him?
You oughtn’t to worry.
“Should” is less common than “ought to”, perhaps due to the pronunciation and the formation of clusters of consonants, e.g. negative form “oughtn’t to.”