English has three common ways to say that something is possible but not certain: may, might, and could. Native speakers use all three constantly when they are unsure about something. Understanding how they differ — and when they overlap — helps teachers explain a very frequent area of confusion and helps students express uncertainty naturally.
Before you start — think honestly about your own teaching and experience.
Look at the examples. Answer each question before reading the explanation — this is how your students will learn too.
Read these sentences. The speaker is not sure about something in each one. What word signals the uncertainty?
All three express possibility — something that is not certain but is possible. The difference in meaning between may and might is very small. In theory: may suggests a slightly higher probability (about 50% or more), while might suggests something slightly less likely. But in practice, most native speakers use them interchangeably for general possibility, especially in informal speech. Could adds a further sense of 'one of several possible options' — it often implies a range of possibilities. In everyday teaching, the most useful thing to say is: may = possible, might = possible (possibly slightly less certain), could = possible (one of several options). All three are followed by the base infinitive with no 'to'.
Now look at these sentences. In some of them, 'could' expresses possibility. In others, it expresses something else. Can you identify which is which?
Context is the key. 'When she was young' is a time signal for past — so could = past ability. 'I'm not sure where she is' — the present uncertainty signals possibility. 'Could you...?' at the start of a sentence signals a polite request. For suggestions and possibility, could appears in present or future contexts without any past time signals. This is exactly the challenge with modal verbs: the same word does different things. The solution: always look at context before deciding what 'could' means. This is a useful habit for students to develop when reading.'
Now look at these two uses of 'may'. Both are common. What does 'may' mean in each case?
'You may use a dictionary' — permission (being allowed). 'May I ask?' — asking permission (formal). 'She may be late' — possibility (she might be late). 'The results may surprise you' — possibility. The way to tell: permission usually involves the verb 'may' with a person as subject doing an action they are requesting or being allowed. Possibility usually involves 'may' with a statement about what could happen or be true. Context makes it clear in almost every case. Note: 'may' for permission is formal — in everyday speech, 'can I?' is much more common. 'May I?' appears in formal situations (exams, official meetings, polite professional contexts).'
| Tense / Form | Use / Meaning | Example | Key time words |
|---|---|---|---|
| May | Possibility — something is possible but not certain (slightly more likely) | She may arrive late — the traffic is bad. | may not |
| May | Permission (formal) — being allowed or asking to be allowed | You may leave now. / May I ask a question? | may not |
| Might | Possibility — something is possible but not certain (slightly less certain than may) | He might know — you could try asking him. | might not |
| Could | Possibility — one of several possible explanations or outcomes | She could be in the staffroom or the library. | couldn't (less common for possibility) |
THE PROBABILITY SCALE — how certain is the speaker?
English modal verbs express different degrees of certainty. For possibility, the rough scale is:
MUST → very strong certainty (deduction — almost sure it is true)
SHOULD → expectation (I predict this is likely)
MAY → possibility (about 50% — it could happen)
MIGHT → possibility (slightly less certain than may — but close)
COULD → possibility (one of several options — sometimes even less certain)
In practice, may and might are used interchangeably in most everyday speech. The scale becomes more important at advanced level (covered in the deduction lesson).
NEGATIVES — an important distinction:
May not = it is possible that something will NOT happen
MAYBE vs. MAY BE:
Maybe (one word, adverb) = perhaps. It goes at the start of the sentence.
Is the speaker uncertain about something in the present or future? → may / might / could. Is the speaker saying something is formally allowed? → may (permission). Does 'could' appear with a past time signal (when I was young, last year)? → past ability. Does 'could' appear at the start of a sentence as a question? → probably a polite request. Is 'to' after may, might, or could? → always wrong — remove it.
Choose the correct word or form. Think about whether the sentence expresses possibility, permission, past ability, or a polite request.
Each sentence contains an error. Write the correct version and explain why — then reveal the answer.
Use this sequence directly in class — guided discovery, no textbook needed. Tap each step to mark it done.
STEP 1 — WHERE IS THE TEACHER? (5 minutes): Tell students that a teacher is absent from school today. No one is sure why or where they are. Ask students to suggest possibilities. Write their suggestions on the board:
STEP 2 — DISCOVER THE STRUCTURE (5 minutes): From the sentences on the board, ask students to identify the verb form after each modal. Elicit: base infinitive. No -s, no 'to', no -ing. Establish the rule — same as all other modals. Write it clearly.
STEP 3 — MAYBE vs. MAY BE (8 minutes): Write these side by side:
STEP 4 — PERMISSION OR POSSIBILITY? (5 minutes): Write these sentences and ask students to identify the meaning of 'may' in each:
STEP 5 — UNCERTAINTY IN EVERYDAY COMMUNICATION (5 minutes): Ask students to think of five things that are uncertain in their school or community right now. They share using may/might/could:
Use directly in class — copy, adapt, or read aloud. No printing needed.
For each strategy, choose the option that best describes where you are now.
Your feedback helps other teachers and helps us improve TeachAnyClass.