probability possibility

Probability, Possibility


Modal auxiliary verbs, along with other parts of speech, can express the probability (certainty, possibility) of something happening, and different conditions, states, and situations.

Terms indicating probability

Modals: must; could, might, may; can’t, couldn’t
Adverbs: definitely, certainly; probably; possibly
Verbs: know; believe; think; doubt

Adjectives: definite, sure, positive, certain; possible

Form of Probabilities, Possibilities: Positive

 Forms of be: be, am, is, are, was, were, been, being  

(+): Subject + must; could/might/may + verb-1.
(-): Subject + might not/may not; can’t/couldn’t + verb-1.
Subject + be + adverb (not) + noun/adjective.
Subject + adverb + be (not) + noun/adjective.
Subject + adverb + (do not) + main verb.
Subject + (do not) + know; believe; think; doubt (that)
Subject + be (not) + definite/sure/positive/certain (that)
Perhaps/Maybe + subject + verb.

Note: saying absolutely, certainly or definitely, does not necessarily mean it is so.

Who might be saying the following to whom? Why did they say that?

Know 1. Everyone knows that it’s a just myth.
Definitely 2. Theirs is definitely the best.
Certainly 3. They certainly talk a lot.
Sure 4. I am sure it was just a bird or a cat.
Positive 5. Bernie is positive he left it right here.
Must 6. Ted and his friends must be exhausted by now.
7. Dr. Ghosh must have a lot of patients.
Believe 8. We all believed she was innocent (not guilty).
Probably 9. Domingo is probably the most qualified.
Think 10. The boss thought the ad was corny. I thought so too.
Could 11. Quiet! This could be a prospect or a client.
Might 12. Unmotivated students might not be the problem.
May 13. The rumours may be true.
Maybe 14. Maybe they are embarrassed or shy.
Perhaps 15. Perhaps her method really works.
Possible 16. It’s possible that someone embezzled the funds.
Probably 17. Jaclyn is probably not interested.
Doubt 18. I doubt that explanation is correct.
Don’t think 19. They didn’t think Maryam was capable.
Can’t be 20. Today can’t be a workday/school day.
Couldn’t be 21. Apendia couldn’t be a poor country.
Certainly 22. They certainly don’t practice enough.
Definitely 23. This definitely isn’t the right way!
Impossible 24. Impossible! That’s impossible!

Respond to the following sentences using words that express certainty, probability, or possibility.


1. Milton’s got a new car. Example: He probably has a rich uncle. Maybe his mother is a doctor.

2. Everyone stares at Mr. and Mrs. Shula when they walk down the street.

3. Johan is smiling to himself.

4. Sherry is 42, but she looks 27. Her cousin is 37…he looks 52.

5. Carlton looks depressed.



6. The town’s population is increasing.

7. The city is awful quiet today. There are hardly any cars or people in the streets.

8. There is a parade with celebrating and a festival in the town centre.

9. It’s getting hotter here.

10. Mr. and Mrs. Baumann have moved to Costa Rica.

School, Work

11. There is a lively, exciting atmosphere in the office/class today.

12. The students/workers are very enthusiastic, motivated, and energetic about their lessons/work.

13. The office/class awful is quiet today; no one is speaking.

14. Mr. Liu has become very successful and prosperous.

15. But his former classmate is always broke and in debt.


16. Nobody here speaks English.

17. The Lightning Football team has a winning record.

18. Look. Some people are protesting there.

19. Many people are emigrating.

20. Many newcomers have moved here recently.


Business, Economics

21. Don’t invest in that scheme.

22. The economy of Cartilagia is booming, while that of Ligamentia is in recession.

23. This restaurant is very popular among city residents.

24. The government has a deficit.

25. That company comes up with great innovations and high-quality products.



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