Modal Verbs: Nuance & Politeness
Use modals to express ability, obligation, permission, advice, and possibility with greater precision.
4.1 — Can, Could, Be Able To: Ability Across Time
4.2 — Must, Have To, Should, Ought To: Obligation and Advice
4.3 — May, Might, Could: Possibility and Uncertainty
4.4 — Must Not vs. Don’t Have To: Prohibition vs. Lack of Obligation
4.5 — Modal Verbs in Questions and Requests (Could you…? Would you…?)
4.1 Can, Could, Be Able To: Ability Across Time
Use can for present or general ability, could for past ability or polite requests, and be able to for all tenses (especially future or after other modals). Can is more common in the present, but be able to is required for specific past successes or future forms.
Form: can / could + base verb — e.g. "I can swim." · "I could swim when I was young." · "I will be able to swim after lessons."| Use | Signal Words | Example |
|---|---|---|
| Present / general ability | now / usually | "I can speak three languages." |
| Past ability | when I was / in the past | "She could run very fast as a child." |
| Future ability | next year / soon | "By June, I will be able to drive." |
| Specific past success | managed to | "I was able to finish the test on time." |
4.2 Must, Have To, Should, Ought To: Obligation and Advice
Use must for strong personal obligation or logical deduction, have to for rules or external obligations. Use should / ought to for advice or recommendations (ought to is slightly more formal). Negative: mustn’t = prohibited; don’t have to = not necessary.
Form: must / have to / should / ought to + base verb — e.g. "You must stop." · "You should see a doctor."4.3 May, Might, Could: Possibility and Uncertainty
Use may and might to express possibility (might suggests less certainty than may). Could can also express possibility or past possibility. Negative forms indicate low probability.
Form: may / might / could + base verb — e.g. "It may rain later." · "She might not come."| Form | Use | Example |
|---|---|---|
| may / might | Future possibility | "It may snow tomorrow." |
| might | Lower certainty | "He might forget his keys." |
| could | General possibility | "You could win if you try." |
| may not / might not | Possible negative | "She might not like the idea." |
4.4 Must Not vs. Don’t Have To: Prohibition vs. Lack of Obligation
Must not (mustn’t) expresses prohibition — something is not allowed. Don’t have to expresses lack of obligation — something is not necessary. They are completely different in meaning.
Form: must not / mustn’t + base verb vs. do/does not have to + base verb| Use | Signal Words | Example |
|---|---|---|
| Prohibition (forbidden) | mustn’t | "You mustn’t use your phone during the exam." |
| No obligation (optional) | don’t have to | "You don’t have to wear a tie — it’s casual." |
| Strong advice against | mustn’t | "We mustn’t be late again." |
| Choice / not required | don’t have to | "Students don’t have to attend the optional lecture." |
4.5 Modal Verbs in Questions and Requests
Use could you...? and would you...? for polite requests (more polite than "can you...?"). May I...? for formal permission. Would you like...? for polite offers.
Form: Modal + subject + base verb? — e.g. "Could you help me?" · "May I use your phone?"Practice Quiz — B1 Level
20 questions selected from a pool of 50 · Modal Verbs: Nuance and Politeness · Click your answer for instant feedback
Choose the correct modal verb to complete each sentence. Think about the nuance — is it ability, obligation, advice, possibility, prohibition, lack of obligation, or a polite request? Click your answer for immediate feedback.