Modals in the present and past
Modal verbs, sometimes called modals, are auxiliary verbs (helping verbs). They express such things as possibility, probability, permission and obligation.
Generally speaking modals in the past have the following form:
- modal + have + past participle
Example:
- Present:
You should see a doctor. - Past:
You should have seen a doctor
Except for modals that express obligation,ability and lack of necessity:
- Obligation:
Present = I must / have to work hard. -- Past = I had to work hard. - Ability:
Present = I can run fast. -- Past = I could run fast when I was young. - Lack of necessity:
Present = You don't have to / needn't take your umbrella. -- Past = You didn't have to / didn't need to take your umbrella.
| Modals in the Present | Modals in the Past | |
|---|---|---|
| Obligation | You must / have to stop when the traffic lights are red. | You had to stop. |
| Advice | You should see a doctor. | You should have seen a doctor |
| Prohibition | You mustn't smoke here. | You mustn't have smoked there. |
| Ability | I can run fast. | I could run fast. now I am old. |
| Certainty | He has a Rolls Royce. He must be very rich. He can't be American. His English is terrible. |
He must have been rich. He had a big house and an expensive car. He can't have written that poem. He was illiterate. |
| Permission | Can I go out? | She could drive her father's car when she was only 15. |
| Possibility | It may / can / could / might rain. It's cloudy. | I guess it may / can / could / might have been Lacy on the phone. |
| Lack of necessity | You don't have to / needn't buy any tomatoes. There are plenty in the fridge. | You didn't have to / didn't need to buy tomatoes. |