Modals of probability are formed the same ways as other modals, but have different meanings. Words such as COULD, SHOULD, MAY, and MIGHT have only one form, and come before the verb:
Statements: MODAL (+ NOT) + VERB:
- Walter MIGHT BE here, but he has probably left.
- I MAY HAVE enough money. Otherwise will you lend me some?
- This SHOULDN'T TAKE long. Can you wait for me?
- Jerry MUST know about the meeting; I mailed him.
- SHOULD ten minutes BE enough time for your appointment? Where MIGHT Sally KEEP her appointment book?
- Modals MAY and OUGHT TO are rarely used in question forms.
Notice the varying degrees of probability:
- John MAY BE at home. (It's possible he's there.)
- He MIGHT BE outside in the garden. (It is a little less possible.)
- He COULD BE at the neighbors. (It's another possibility - COULD is used more and more as a synonym of MAY or MIGHT in colloquial English)
- John SHOULD BE at home. (That's where I expect him to be.)
- He OUGHT TO BE expecting us. (He probably is. SHOULD & OUGHT TO are almost synonymous)
- John MUST BE at home. (I just spoke to him on the phone. This is a deduction. I'm almost certain because of the evidence.)
- John COULDN'T BE at home! (I know he's out of town until tomorrow.)
I've looked for Edgar everywhere. Do you think he __________ be out to lunch?
must
might
should
ought to
We'd better hurry back or they _________ tow the car away.
must
may
should
ought to
Where __________ ? I thought it was in my pocket.
must my wallet be
should my wallet be
may my wallet be
could my wallet be
Gina _______ work long hours. She never has time to enjoy herself.
may
must
should
might
I always see John walking around town. He __________ have a car.
must not
might not
couldn't
shouldn't
Mary _________ know about the meeting. She was he one who sent out the memo about it.
may
could
must
might
I've never eaten at Mario's, but they _________ have a children's menu. It's a family restaurant and lots of people take their kids there.
could
should
may
might
I just heard that the flight __________ leave on time due to stormy weather.
may not
should not
must not
ought not to
Is that Tom sitting in that car over there? Surely not. It ______ be Tom. He would never wear a hat like that!
may not
mustn't
couldn't
mightn't
Where _________ a paper shop that sells foreign magazines?
must I find
can I find
should I find
ought I to find
Bill says he _________ go to Italy for his holidays but he hasn't decided for sure yet.
should
may
ought to
must
If you go to Morocco expect the days to be warm at this time of year. However, it ____________ cool off at night.
should
could
may
must
Janet still hasn't got her passport! It __________ be ready by now. She applied for it more than six weeks ago.
could
may
might
ought to
This is the third time Laura has been late this month. What ________ think of her ?
may her boss
ought her boss to
might her boss
must her boss
Why has Paula been down to the employment agency? Well, I know she doesn't like her new boss. I guess she _________ be looking for a new job.
must
may
ought to
should
Why don't we drive ? I'm afraid there ________ be any cabs at this time of night.
might not
must not
couldn't
shouldn't
I don't see Ken anywhere in the office. I saw him a few minutes ago though so he _________ be around somewhere!
must
could
should
might
No one named Frank works in this office. We only have two offices and the other is at Putney. If you are sure he's with the company, he _________ work there.
ought to
must
should
may
The moon looks so big and round. It __________ be full tonight.
might
could
must
should
Otto said he'd be here at 8h.00 and it's five to eight. He __________ arrive any minute now.
might
must
should
may
The drive from here to Boston __________ take more than two hours, unless traffic is heavy.
mustn't
shouldn't
couldn't
mightn't
The delivery should arrive at ten o'clock but with all this snow it ______ take a lot longer!
must
might
should
ought to
I have taken two asprins for my headache. It ___________ go away in a few minutes.
ought to
must
could
may
William is always expensively dressed and he drives a fast sports car. He ________ earn a lot of money.
might
must
should
may
Let me write down your last name or I __________ remember how to spell it.
should not
must not
could not
might not
Not many people think George's idea will work, but a test wouldn't cost much. I guess we ________ try it.
must
may
could
might
Getting a car stereo installed ____________ be too expensive. Mine wasn't and they are getting cheaper all the time. Why don't you check?
shouldn't
mustn't
may not
might not
I ______ be a little late for the meeting. I'm having a lunch with a client just before and you know how it goes; you can't always get away on time.