Modal Verbs: Can, Could, May & Might

At C1, can, could, may, and might express more than simple ability or permission. This lesson compares their uses for possibility, deduction, politeness, and register.

These modals can help speakers sound:

• nuanced
• careful
• diplomatic
• academically precise

1. Advanced Uses of “Can”

1.1 General/theoretical possibility

Used to describe what is sometimes possible.

Examples

• Accidents can happen at any time.
• Success can be difficult to maintain.
• Online communication can create misunderstandings.

This use describes:

• general truths
• theoretical possibility

1.2 Characteristic behaviour (often evaluative/critical)

Examples

• She can be extremely impatient.
• He can be difficult to work with.

This use describes someone’s typical tendencies; it can sound critical depending on context and intonation.

This often expresses:

• criticism
• evaluation

1.3 Negative deduction with “can’t”

In epistemic uses, can’t/cannot expresses a strong conclusion that something is impossible or not true. This is different from can’t for lack of ability.

• Present deduction: “That can’t be true.”
• Present situation: “She can’t be working today; the office is closed.”
• Past deduction: “She can’t have finished already.”

Use can’t + base form for a present conclusion and can’t have + past participle for a conclusion about the past.

2. Advanced Uses of “Could”

2.1 Tentative possibility

Less certain and softer than “can.”

Examples

• It could rain later.
• This could be the solution we need.
• There could be another explanation.

“Could” often sounds:

• cautious
• analytical
• less direct

2.2 Suggestions and diplomacy

Examples

• We could try another approach.
• You could ask for more clarification.
• Could I make a suggestion?

This creates:

• politeness
• cooperation
• softer interaction

In suggestions, ‘could’ offers an option (‘We could…’). In other contexts it can describe conditional possibility (‘It could work if we had more time’).

2.3 Past possibility: could have

For a specific completed past event, use could have + past participle, not could + base form:

• ✗ “He could be at home yesterday.”
• ✓ “He could have been at home yesterday.”

Could can describe a present, future, general, or conditional possibility, but could have looks back at a completed past situation.

3. Advanced Uses of “May” and “Might”

3.1 Uncertain possibility

Examples

• She may be at home.
• They might not agree with the proposal.
• The results may vary.

“May” often sounds:

• slightly more formal
• can signal a cautious, neutral possibility

“Might” often sounds:

• more tentative
• less certain

Compare the same possibility in two contexts:

• Neutral/formal report: “The committee may approve the proposal.”
• Tentative conversational comment: “They might approve it, but I’m not sure.”

This is a difference in tone, not a fixed difference in probability; either modal may be possible in the same situation.

3.2 Formal and academic style

Examples

• These measures may improve productivity.
• Economic conditions might affect consumer behaviour.

Common in:

• academic writing
• formal discussion
• reports

Two useful C1 collocations are:

• may well = a fairly likely possibility: “It may well be the best option.”
• might as well = the sensible thing to do when there is no better alternative: “We might as well start without her.”

3.3 Concessive may and might

May and might can introduce a concession rather than a possibility:

• “He may be the boss, but he is still wrong.”
• “She might be young, but she knows what she is doing.”

3.4 Past possibility: may have and might have

Use may/might have + past participle for an uncertain past explanation:

• “She may have missed the train.”
• “They might have already left.”

As with present possibility, may have often sounds more formal and might have more tentative, but the difference is not fixed.

4. Degrees of Certainty

These are tendencies in epistemic (possibility) uses; context can override them.

Epistemic = about how sure the speaker is (guessing, estimating, concluding), not about ability or permission.

Form	Epistemic meaning	Example
can	general possibility or tendency; not normally the probability of one specific event	“Technical problems can occur.”
can’t / cannot	strong deduction that something is impossible or untrue	“That can’t be the answer.”
could	a possibility, often tentative or conditional	“There could be another explanation.”
couldn’t	strong past deduction or stated past impossibility; can’t have is the usual present-perspective deduction	“He couldn’t have sent the message; he had no internet.”
may	a possibility, often neutral or formal	“The results may change.”
may not	it is possible that something is not true or will not happen	“The results may not be accurate.”
might	a possibility, often tentative	“The plan might work.”
might not	a tentative possibility that something is not true or will not happen	“The plan might not work.”

May not and might not usually mean “perhaps not” in epistemic contexts. May not can instead mean “not permitted” in a permission context: “Visitors may not enter this area.” Context makes the meaning clear.

5. Politeness and Softening

These modals help avoid sounding too direct.

Examples

• Could you explain that again?
• May I ask a question?
• You might want to reconsider that.

Mini-notes:

• “Could you…?” = polite request.
• “May I…?” = formal permission.
• “You might want to…” = softened suggestion/advice (can imply mild criticism; use carefully).

6. Summary

• “Can” for general/theoretical possibility and for characteristic tendencies (often evaluative).
• “Can’t” for a strong deduction that something is impossible or untrue; use can’t have + past participle for past deduction.
• “Could” for tentative possibility and diplomatic suggestions; use could have for a specific completed past possibility.
• “May/might” for uncertainty, including may/might have for the past and concessive uses; “may” is often more formal, while “might” is often more tentative.
• Certainty differences are context-dependent rather than fixed.
• These modals can soften requests and recommendations, so they affect tone as well as grammar.