3.1: Modal Verbs Expressing Degrees of Certainty
- Page ID
- 273142
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Introduction - Modal Auxiliary Verbs
Modal Auxiliary Verbs are a very rich area of the English language. They are used with great frequency and with a wide range of meanings.
| can | could | may | might |
| would | will | should /ought to | must |
All of them can express degress of certainty, probability or possibility of an event. But they can also express ideas such as willingness and ability, permission and refusal, obiligation and prohibition, suggestion, necessity, promise and intention.
Modal Verbs expressing certainty, probability or possibility
In order of certainty:
WILL and WON'T are used to predict a future event or action which are seen as certain. The truth or certainty of what is asserted is more or less taken for granted.
- I will see you later.
- His latest book will be out next month.
MUST is used to assert what we infer or conclude to be the most logical or rational interpretation of a situation or event. As we do not have all the facts, it is less certain than will. The negative form is CAN'T or COULDN'T
- He walked across the Sahara desert! You must be joking!.
- She can't have a ten-year-old daughter! She's only twenty-five herself!
- He couldn't be working right now. He went on vacation yesterday.
SHOULD expresses what may reasonably be expected to happen. Expectation means believing that things are or will be as we want them to be. This use of SHOULD carries the meaning of "if everything goes according to the plan, then something should happen"; therefore it doesn't suggest negative or unpleasant ideas.
- You have worked hard. You should pass the exam.
- If the flight is on time, he should arrive in Jakarta early this morning.
MAY and MIGHT and COULD express the possibility that something will happen or is already happening.
- We may go to Spain this year. We haven't decided yet.
- A: "Where's Sandra?" B: "I don't know. She may be taking a bath".
- I might not be back in time for supper, so don't wait for me.
- They might be eating dinner now. We should call them later.
- It could be expensive to keep a dog (if we had one, it could or it may not be expensive)
- Mark could be at the park. He said he was going to go for a run.
- We could stay with Jessica in London (it's possible, if she's there)
Be careful with could. It also has the meaning of past ability such as in this example:
- He could ride a bike when he was 5 years old.
Could not is not used to express a future possibility. The negative of could is MIGHT NOT.
- It might not be right.
- He might not be working today.
Couldn't has a similar meaning to can't, but only slightly weaker. It expresses a near impossibliity.
- She couldn't have a ten-year old daughter! She's only twenty-five herself!
- Joe can't be in his office. He just started a meeting a few minutes ago.
OUGHT TO, as well as SHOULD, + HAVE + PAST PARTICIPLE are used to talk about an expectation that something happened, has happened, or will happen.
- If the flight was on time, he should/ought to arrive in Paris early this morning.
- The builders should/ought to finish by the end of the week.
- Maria should be studying* right now.
*Should and ought to are also used to express advice. The meaning can be ambiguous (unclear) as in this example.
Summary: Degrees of Possibility
We can express certainty with modals of possibility. If you are 100% certain, then no modal is necessary, but if you’re almost certain then use the modal must. If you’re less than 50% certain, then use may, might, or could.
When your teacher is absent, you might infer these possibilities:
She is sick. (100% certain)
She must be sick. (95% certain)
She should be there. (Expectation)
She may be sick. (less than 50% certain)
She might be sick. (less than 50% certain)
She could be sick. (less than 50% certain)
For more information on this topic, watch these videos: Modals of Possibility- May, Might, and Could and Modal of Certainty-Present
Exercise 3.1.1-Inference Practice
Below is a list of situations. Give one sentence with must for a strong inference (guess), and write another sentence with a less likely possibility. Use the example to guide you.
Example: Your teacher’s eyes are red.
95% certain: She must have allergies.
Less than 50% certain: She might have an eye disease.
1. Class started at 8:00. You arrived at 8:30 and the classroom is empty.
2. Your classmate is using crutches.
3. There's a different teacher sitting at the teacher's desk today.
4. Your classmate is sad after receiving her exam results.
5. Your classmate is coughing.
6. Your friend is carrying a beach towel and wearing a swimsuit.
7. You hear a loud noise in your garage.
8. You hear an ambulance.
9. Your son received a high grade on his math test.
10. The traffic is stopped, and you see a police car on the corner.
Exercise 3.1.2: Rewrite the Sentence
Rewrite the sentences with the choices given and then check your answers below.
Example:
Perhaps she works
A. may B. could
Answer
A. She may work B. She could work.
1. Maybe he plays the piano.
A. might B. may
A. ___________________________ B. ___________________________
2. Perhaps she sees us.
A. may B. might
A. ___________________________ B. ___________________________
3. This street is unfamiliar. It appears like we are lost.
A. must
A. ___________________________
4. Maybe she lives here
A. might B. may
A. ___________________________ B. ___________________________
5. I believe he is in his office.
A. should
A. ___________________________
6. It is possible that she is not home.
A. may B. might
A. ___________________________
8. It is not possible for her to be a teacher.
A. can't B. couldn't
A. ___________________________ B. ___________________________
9. I believe she is working now.
A. should
A. ___________________________
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