Modality options

Auxiliary verbs

• Be

• Can

• Do

• Have

• May

• Must

• Ought

• Shall

• Will

Modal auxiliaries broad categories

• Possibility/Permission

• Necessity/Obligation

Modal auxiliary verbs

Modal Auxiliary	Present Neutral	Present Negative	Past Neutral	Past Negative
can	can	cannot / can’t	could	could not / couldn’t
may	may	may not	might	might not
must	must	must not / mustn’t	— (no true past form)	—
shall	shall	shall not / shan’t	should	should not / shouldn’t
will	will	will not / won’t	would	would not / wouldn’t
ought	ought (to)	ought not (to)	— (no distinct past form)	—
need (modal use)	need	need not / needn’t	—	—
dare (modal use)	dare	dare not / daren’t	—	—

Note

Modals have only present and past tense, no participles, no plain form

Shall is used, but rarer.

Would reflects remoteness

May is often used to describe something as possibly true in the sense of being compatible with everything we know

There may be no integer solution to this equation

Modality

Modality	Meaning	Example sentence
Ability	Subject has the capacity to do something, freedom to do something	She can swim.
Possibility	Something is possible but not certain	She may arrive later.
Probability	Speaker judges something as likely	He should be home by now.
Prediction	Speaker predicts a future situation	They will win the match.
Firm Prediction	Firm prediction	We shall overcome.
Soften Prediction	Not as past, but reduced assertion	We should be all right.
Permission	Allowing someone to do something	You may leave early. You can go now. Can I kiss you? You may kiss me now.
Obligation	Something is required	You must wear a helmet.
Moral or Ethical Obligation	Duty or obligation	You ought to be careful. You should be more careful (here should is another lexeme, not past of shall)
Determinism, no choice	inner determination, commanding	You will do as I say. I will get this done
Prohibition	Something is not allowed	You must not park here.
Advice	Speaker recommends something	You should see a doctor.
Volition / Willingness	Subject is willing or determined	I will help you.
Necessity	Something is logically required	This must be the place. You needn’t wear shoes
Epistemic Necessity (logic inference)	Strong logical inference, based on evidence	There must be something wrong with mechanism

Common uses of should

Use	Example
Advice	You should see a doctor.
Weak obligation	Students should submit the form today.
Expectation / probability	The train should arrive soon.
Subordinate clause (mandative)	They insisted that he should resign.

Common uses of would

Use	Example
Conditional	I would go if I had time.
Polite requests	Would you help me?
Past habitual	When we were children, we would swim in the river.
Volition	He would not listen.

Lexical verbs carrying modality

Common:

Lexical verb	Modality type	Typical meaning	Example
seem	Epistemic (evidential)	Appearance, epistemic possibility	She seems to understand.
appear	Epistemic (evidential)	Appearance, inference	He appears to be upset.
look	Epistemic (evidential)	Evidential appearance	It looks as if it’s going to rain.
sound	Epistemic (evidential)	Evidential appearance	That sounds reasonable.
suggest	Epistemic (evidential)	Evidence leading to inference	The results suggest that the treatment works.
indicate	Epistemic (evidential)	Evidence supporting a conclusion	The data indicate that demand is falling.
imply	Epistemic (evidential)	Indirect evidence	His silence implies agreement.
predict	Epistemic	Future expectation	Experts predict inflation will fall.
expect	Epistemic	Expectation	We expect prices to rise.
believe	Epistemic	Personal epistemic stance	I believe he is right.
think	Epistemic	Personal judgement	I think she’s correct.
suppose	Epistemic	Tentative judgement	I suppose it could work.
doubt	Epistemic	Low probability	I doubt they’ll agree.
hope	Bouletic (desire)	Desirability + possibility	We hope to finish today.
fear	Bouletic (negative expectation)	Negative expectation	I fear we are too late.

Note

“Hope” and “fear” are often treated as bouletic (desire-related) rather than purely epistemic, because they express what is wanted or dreaded rather than simply how likely something is.

Fear also carries an epistemic implication (the speaker thinks the event is plausible), but its primary modal flavour is desirability.

By semantic group:

Group	Verbs
Appearance / evidentiality	seem, appear, look, sound
Evidence-based inference	suggest, indicate, imply
Belief / judgement	think, believe, suppose, doubt
Prediction / expectation	predict, expect
Hope / fear	hope, fear

Epistemic:

Degree of certainty	Modal auxiliary	Lexical verb equivalent	Example
High certainty / Deduction	must	demonstrate, prove, establish, deduce, confirm	Modal: The system must fail. Lexical: The data demonstrates that the system is failing.
Probability / Expectation	should	project, anticipate, expect, suggest, tend	Modal: Prices should stabilize soon. Lexical: Analysts project that prices will stabilize soon.
Possibility / Appearance	may, might	appear, seem, imply, indicate, hint	Modal: The theory might be wrong. Lexical: The theory appears to be wrong.
Speculation / Suspicion	may	suspect, speculate, hypothesize, surmise	Modal: He may have hidden motives. Lexical: Critics suspect he has hidden motives.
Contested claim	would	claim, purport, profess, assert	Modal: It would solve the issue. Lexical: The reform purports to solve the issue.

Deontic:

Modality type	Modal auxiliary	Lexical verb equivalent	Example
Obligation	must	require, compel, oblige, demand, dictate	Must: Citizens must pay taxes. Lexical: The law compels citizens to pay taxes.
Prohibition	must not	forbid, prohibit, ban	Modal: You must not enter. Lexical: Security policy prohibits entry.
Permission	may	permit, allow, authorize	Modal: You may proceed. Lexical: The committee authorizes you to proceed.

Dynamic:

Modality type	Modal auxiliary	Lexical verb equivalent	Example
Ability / Success	can	manage, succeed, possess (the capacity)	Modal: She can solve the equation. Lexical: She managed to solve the equation.
Inability / Failure	cannot	fail, struggle, lack (the capacity)	Modal: The bridge cannot hold the weight. Lexical: The bridge fails to support the weight.
Capacity / Tendency	will	tend, enable, foster	Modal: Institutions will protect themselves. Lexical: Institutions tend to protect themselves

See also

Speculation