Verbs can be classified by function into two types:
Lexical verbs: go, teach, learn, walk, get, buy, etc.
Auxiliary verbs. These can in turn be classified into three types:
Primary auxiliaries: do, have, be.
Modal auxiliaries: can, could, will, would, shall, should, may, might, must, ought to.
Semi-modal auxiliaries (also called periphrastic modals): need, dare, used to. would rather, had better.
To understand ‘modal auxiliary verbs’ better, let us first compare them to ordinary verbs.
Note.
Modals never take the infinitive to: *to must/ *to will
They never add the –s to third person singular in the present: *he cans/ *she mays
They never require the –ed ending for the past: *shoulded
They never use forms of do or be to make negatives, yes/no questions, or tag questions: *you don’t can; instead, they use the word not for the negative: you cannot, she should not. They are used before main verbs, in tags and short answers as in these examples:
-A: You can speak French, can’t you? -A: You shouldn’t be here, should you?
B: Yes, I can. B: No, I shouldn’t.
All modals can refer to the present or the future using the same form, and what is commonly called the past form of modals like ‘could, would’ is not really the past.
-Could you give me a ride to university tomorrow?
These forms are truly the past when they are clarified with additional information or through context.
-They couldn’t attend the meeting yesterday.
Modals can have different meanings depending on what we want to express: ability, permission, possibility, etc. This is considered in details in this chapter.
1. ABILITY.
A. Can is used to talk about ability in the present.
-She can analyze people’s handwriting.
-He can’t afford to pay the bill. (He doesn’t have the ability …)
-She can do computer graphics.
We use can for the future if we are deciding now what to do in the future.
-If we earn some money, we can go on holiday next summer.
-We can take samples of the lake water tomorrow.
B. Be able to.
-The kids are able to use the computer. (Present)
-Helen is able to read well, even though she’s only three. (Present)
-By June she will be able to complete her computer class. (Future)
-I’m afraid I won’t be able to come to the disco on Friday. (Future)
-Souad was able to play the piano when she was six. (Past)
-I wasn’t able to do one problem. (Past)
C. Could is used to express an ability or opportunity in the past.
-The children could swim when they were quite young.
-After only six months, Ann could play the violin quite well.
-They had a car, so they could travel very easily.
Could is also used for ability in unreal conditions.
-If you spoke a foreign language, you could get a better job.
-If I had time I could help you.
Notice.
- (Use only was/ were able to to talk about specific achievement or a single event in the past. (ability + a particular action).
-Amine was able to win the Math Prize last year.
-Luckily, Mark was able to get the work done in time. (succeeded in getting … )
-The drivers were able to stop before they crashed into each other. (managed to …)
- (Use either could or was/ able to in negative sentences and questions.
-It was foggy, so the plane couldn’t/ wasn’t able to take off.
-Could you/ Were you able to describe the man to the police.
- (For forms and tenses other than the present or the past use be able to.
-It’s nice to be able to go to the opera. (To-infinitive)
-We were very lucky to be able to live in the country during our childhood.
-It’s been quiet today. I’ve been able to get some work done. (Present perfect)
-Since he left, none of the other team members have been able to match his
enthusiasm.
So useful
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