English Modal Verbs: Ability, Possibility, Obligation, and More

Ability

Expressing ability with modal verbs:

• Can (present ability): Can you speak French?
• Will be able to (future ability): She will be able to speak French in two months.
• Could (past ability, unrealized potential): I could have gone to university when I was younger.
• Be able to (general ability): She is able to speak Chinese.
• Was/were able to (past ability, achieved action): We were able to escape the fire.
• Couldn't/were not able to (negative past ability): We couldn't/were not able to finish the project.

Possibility

Expressing degrees of possibility:

• May (higher probability): He may be in his office.
• Might (lower probability): She might be 30 years old.

Certainty

Expressing certainty or impossibility:

• Must (certainty): He must be over 70.
• Can't (impossibility): She can't be at university; she is only 15 years old.

Requests and Permissions

Making requests and asking for/giving/refusing permission:

• Could you (polite request): Could you tell me how to get to the bus station?
• Can you (informal request): Can you help me with this?
• Can/Could/May (asking for permission): Can/Could I borrow your bicycle? May I come in?
• Can (giving permission): You can smoke if you like.
• You are not allowed (refusing permission): If you are under 17, you are not allowed to drive a car in Britain.

Obligation, Prohibition, and Lack of Obligation

Expressing obligation, prohibition, and lack of necessity:

• Must/Have to (obligation): You must/have to have a passport to travel internationally. I had to go to the hospital. Many children in Britain have to wear a uniform.
• Must have (past obligation): You must have had a passport to visit then.
• Mustn't (prohibition): You mustn't tell anyone what I said. You mustn't forget what I told you; it's very important. You mustn't talk in class.
• Don't have to (lack of obligation): I can hear you clearly; you don't have to shout. You don't have to hurry; we have plenty of time. The exhibition was free, so I didn't have to pay. We have lots of time; we don't have to rush.

Advice

Giving advice or recommendations:

• Should/Shouldn't: You have been coughing a lot; you shouldn't smoke so much. You should give up smoking. People should talk less and listen more. I think you shouldn't go there. The government should invest more in education.

Practice Exercises

Complete the sentences with the appropriate modal verb:

1. You don't have to hurry. We have plenty of time.
2. The exhibition was free, so I didn't have to pay.
3. She is allergic to dairy products, so she mustn't eat any.
4. People should talk less and listen more.
5. The boy was able to/could escape.
6. I think you shouldn't go there.
7. We tried, but we couldn't/were not able to open the door.
8. The government should invest more in education.
9. I can hear you clearly; you don't have to shout.
10. We have lots of time; we don't have to rush.