Modals and passive voice
Modal verbs of ability, obligation and deduction, and the passive in simple tenses
Modal verbs such as can, could, may, might, must, should and ought to add meaning to the main verb, and they are always followed by the bare infinitive (the base verb with no 'to' and no -s): 'She can swim', not 'She can to swim' or 'She cans swim'. We use can/could for ability, permission and requests, may/might for possibility, must for strong obligation or for a confident deduction, have to for an obligation that comes from outside, and should/ought to for advice. Be careful with negatives: 'mustn't' means something is forbidden, while 'don't have to' and 'needn't' mean there is no necessity to do it. The passive voice is formed with the verb 'be' plus the past participle (V3): in the present simple it is am/is/are + V3 ('English is spoken here'), and in the past simple it is was/were + V3 ('The house was built in 1990'). We use the passive when the action or the result matters more than the person who does it, and we can name the doer with 'by'. When we change an active sentence into a passive one, the object of the active sentence becomes the subject of the passive sentence. For example: active 'Workers built the bridge in 1995' becomes passive 'The bridge was built by workers in 1995'.
Key terms
| Modal | Meaning | Example |
|---|---|---|
| can / could | ability | She can play the piano very well. |
| must / have to | obligation | You must wear a seatbelt. |
| mustn't | prohibition | You mustn't smoke in the hospital. |
| should / ought to | advice | You should see a doctor. |
| might / may | possibility | Take a coat; it might rain later. |
| Tense | Passive form | Example |
|---|---|---|
| Present simple | am/is/are + V3 | English is spoken here. |
| Past simple | was/were + V3 | The house was built in 1990. |
| With modals | modal + be + V3 | The results will be announced tomorrow. |
- 1Active sentence: Workers built the bridge in 1995.
- 2Find the object: The object 'the bridge' receives the action, so it becomes the new subject.
- 3Form 'be' + V3: The action is past simple, so use 'was' + the past participle 'built': 'was built'.
- 4Add the agent with 'by': Passive: 'The bridge was built by workers in 1995.'
- 1Read the situation: It's a sunny day, so we ___ take an umbrella.
- 2Decide the meaning: An umbrella is simply not necessary; it is not forbidden, so 'mustn't' is wrong.
- 3Pick the modal: Use 'don't have to' for no necessity: 'we don't have to take an umbrella'.
A modal is followed by the bare infinitive: write 'must finish', not 'must to finish' or 'musts finish'. Modals never take 'to' and never add -s.
'Mustn't' is not the same as 'don't have to'. 'Mustn't' means it is forbidden; 'don't have to' (and 'needn't') means it is simply not necessary, so there is a choice.
The passive always needs 'be' + the past participle (V3), not the past simple: write 'was stolen', not 'stole' or 'was stole'. Name the doer with 'by'.
Make the passive 'be' agree with the new subject: 'Cars are made' (plural) but 'A new school is opened' (singular).
Rules
- 1Modals (can, could, may, might, must, should, ought to) are followed by the bare infinitive: 'must go', not 'must to go' or 'musts go'.
- 2Use must for strong obligation or a confident deduction ('He must be tired'), have to for outside obligation, and should/ought to for advice.
- 3'Mustn't' = it is forbidden (prohibition); 'don't have to' / 'needn't' = it is not necessary, so there is a choice.
- 4Form the passive with be + past participle (V3): present simple am/is/are + V3, past simple was/were + V3; add 'by + agent' to name the doer.
- 5To make a sentence passive, move the active object to the front as the new subject and put the verb into the matching 'be + V3' form.
Practice
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