Why we need the middle of the scale
When you do not want to present an unverified explanation as fact, use might, could or may. They let you say “this is possible”, leaving room for other explanations.
The choice shows the speaker’s assessment based on available information and context. One person may be confident, while another knows less or deliberately speaks more cautiously. A modal by itself does not establish an event’s objective probability.
First decide whether you are presenting a fact, a confident deduction or only a possible explanation. Might, could and may are common ways to express the third case.
Daniel might be in the meeting room.
Daniel might be in the meeting room.
The speaker can see only a closed door. This is one possibility, not an established location.
The delay could be a network problem.
The delay could be a network problem.
Could presents one of several plausible causes and leaves room for others.
Some services may be unavailable tonight.
Some services may be unavailable tonight.
An official notice honestly warns of a possibility without promising an outage.
Form: a modal plus the base form
Might, could and may are modal verbs. They take the base form: no third-person -s, no to, and no was, has or had. The subject does not change the modal: I might, she might, they might.
Form a negative with not immediately after the modal: might not, may not. Form a question through inversion: Could this be…? Auxiliary do is neither needed nor used here.
Use be for a state, the verb itself for an action, and be + -ing for something that may be happening right now. Have after a modal also takes its base form; with present possession it simply means “possess”, rather than being part of a perfect construction.
subject + might / could / may (+ not with might/may for “possibly not”) + base form (be / have / V / be + V-ing)
- subject / S —
- The grammatical subject: who or what the clause is about; the verb agrees with it. In The book was written, the book is the subject, although someone else does the action.
- verb / V —
- A word for an action or state, such as work or be. The pattern determines its form.
- V1 / base form —
- The base verb without to: work, go, be.
- V-ing / -ing —
- The verb form ending in -ing: working, going. Its role depends on the construction.
Marko might know the door code.
Marko might know the door code.
After might, use know, not knows: the modal does not allow a third-person ending.
She might have a spare key in her bag.
She might have a spare key in her bag.
Have here is ordinary possession in its base form. Might has is impossible.
They could be sitting in the garden.
They could be sitting in the garden.
Be + -ing shows an action that, in the speaker’s view, may be in progress right now.
It may rain before the evening.
It may rain before the evening.
There is no to between may and rain: modals combine directly with the base form.
Three words with roughly the same meaning
In many affirmative sentences about possibility, might, could and may express similar meanings. None specifies an exact percentage of probability. However, do not mechanically extend this interchangeability to every meaning, negative or question.
The difference worth noticing concerns tone and register. May sounds more official and is natural in notices, instructions and customer correspondence. Might can sound the most cautious of the three in conversation. Could often presents an explanation as one of several options worth checking.
These are tendencies, not strict rules. If a task asks for a particular modal, practise that one. In your own text, choose a natural option according to meaning and tone.
The report might be ready by Thursday.
The report might be ready by Thursday.
A cautious conversational possibility: the speaker clearly makes no commitment.
Delivery may take longer than usual this week.
Delivery may take longer than usual this week.
May sounds natural in an official message to customers.
The noise could be coming from the ventilation.
The noise could be coming from the ventilation.
Could offers one explanation that still needs checking.
Now, right now and what lies ahead
This construction covers three time perspectives, none of which requires a different modal. A state now: might be + place, state or characteristic. An action right now: might be + -ing. A future event: might + verb with a future time expression.
Will often expresses a prediction with greater stated confidence and can also express a decision or promise. Might, could and may leave the possibility open. It will rain and It might rain therefore differ in the strength of the prediction.
Tomorrow, later and next week help indicate the future. Time may also be clear from the conversation: you do not have to add a separate marker to every sentence.
The office may be closed at lunchtime.
The office may be closed at lunchtime.
A current or recurring state: the speaker has not checked the schedule.
Anna could be waiting downstairs right now.
Anna could be waiting downstairs right now.
Be + -ing ties the guess to this moment.
The road works might continue until the end of the month.
The road works might continue until the end of the month.
A future event; the time expression makes the future reference explicit without changing the form.
Negatives: “possibly not” versus “certainly not”
The negative possibility forms are might not and may not. They mean “perhaps this will not happen” and retain the same uncertainty as the affirmative. The speaker simply considers the opposite outcome.
Can’t and couldn’t in their impossibility meaning reject an explanation, whereas might not/may not merely allow a negative possibility. That can’t be her number and That might not be her number express different confidence levels. Information can be checked after either one: the speaker can also be wrong.
For ordinary “possibly not”, put not after the modal: might not be, may not know. Negation can also belong to a separate phrase; do not move it mechanically, since that can change the emphasis or meaning.
might not / may not + base form = possibly not · can’t (couldn’t) + base form = certainly not
- V1 / base form —
- The base verb without to: work, go, be.
The parcel might not arrive today.
The parcel might not arrive today.
The speaker considers a negative outcome without asserting it.
They may not know about the change of time.
They may not know about the change of time.
Not comes between may and the base form know.
There might not be enough seats for everyone.
There might not be enough seats for everyone.
In a there + be construction, not also goes immediately after the modal.
Intensifiers: when an explanation becomes very plausible
Sometimes a speaker wants to show that an explanation is not merely possible but quite likely, without moving to a confident deduction. To do this, put an adverb after the modal: might well, may well, could easily, could well.
Well after a modal makes the situation sound noticeably more likely. Could easily works similarly and is particularly natural with duration, cost or quantity: “this could easily take three weeks”.
The usual pattern for “quite possibly” is might/may/could + well + verb. In could easily last, easily also strengthens possibility rather than describing how easy a task is. Adverb position depends on meaning; could be easily repaired, for example, can mean that repairing it would be easy.
might / may / could + well / easily + base form
- V1 / base form —
- The base verb without to: work, go, be.
The delay could easily last another hour.
The delay could easily last another hour.
Easily increases the expressed likelihood, but the sentence remains an assessment, not an announcement.
The library might well be closed by six.
The library might well be closed by six.
Well between might and be strengthens the possibility: “quite possibly”.
This invoice may well be a mistake.
This invoice may well be a mistake.
The more official register of may combines well with the intensifier.
Questions and short responses
For an ordinary question about a possible explanation, use Could this be…? Questions with might are often more formal. May in direct questions most often concerns permission, so could is usually more convenient for neutrally checking an explanation.
The most common conversational way to ask for someone else’s guess is to embed it in a question with do you think: Do you think she might come? The order inside remains declarative, without inversion.
In a short answer, you can leave just the modal: It might, They could. After a question with be, retaining be is natural: She might be. Depending on context, shorter She might is also possible; repeating be is not an absolute requirement.
Could this be another network problem?
Could this be another network problem?
Inversion with could is a standard way to ask about a possible explanation.
Do you think Andriy might join the review?
Do you think Andriy might join the review?
After do you think, the order is declarative: Andriy might join.
— Will the shop still be open? — It might be.
— Will the shop still be open? — It might be.
The short answer repeats the modal and be, omitting the rest.
Scope: what is not covered here
The strong ends of the scale — must for a confident deduction and can’t for confident rejection — belong to a neighbouring rule in the same topic. They appear here only as a contrast, showing when the speaker regards the evidence as sufficient and when not.
Guesses about past events with might/may/could have + V3 are covered separately. Here we practise a possible present state, current process or future event.
Three other neighbouring uses are easy to confuse because of their form. May for permission (You may leave now) is another function of the same word. Can for general possibility (Trains can be busy on Fridays) describes what happens in general, not one specific case. Could for past ability (I could swim at five) is also unrelated to guessing. Context shows which meaning applies each time.
That must be the courier; nobody else has the gate code.
That must be the courier; nobody else has the gate code.
The speaker regards this information as sufficient for a confident deduction; must itself does not guarantee that the deduction is correct.
Trains can be busy on Friday evenings.
Trains can be busy on Friday evenings.
Can describes a general pattern, not a guess about a particular train today.
You may leave your bag at the reception.
You may leave your bag at the reception.
The same may, but a different function: permission, not an assessment of probability.
Common mistakes
Incorrect:She might has a spare key in her bag.
Correct:She might have a spare key in her bag.
A modal always takes the base form. Has is impossible here, whether as ordinary possession or as part of another construction.
Incorrect:It may to rain before the evening.
Correct:It may rain before the evening.
There is no to between the modal and verb: may rain, not may to rain.
Incorrect:He could knows the door code.
Correct:He could know the door code.
The third person does not add -s after a modal: the modal occupies the finite verb position.
Incorrect:There might not is enough space for everyone.
Correct:There might not be enough space for everyone.
After might not, use base be, not is.
Incorrect:I might well to send the draft today.
Correct:I might well send the draft today.
The intensifier well does not introduce a to-infinitive: it is still followed by the base form without to.
Incorrect:Do you think she might comes to the review?
Correct:Do you think she might come to the review?
Inside a question with do you think, word order is declarative, but the modal still requires the base form.