Modal verbs are auxiliary verbs that express ability, possibility, permission, or obligation. They do not change form (no -s in third person) and are followed by the base form of the main verb.
• Can you swim? ✓ (Not: Can you swims?)
• She could read when she was four.
• They will be able to come tomorrow.
📝 2. CAN - Present Ability & Permission
Uses of CAN:
✅ Present Ability (Skills & Capabilities)
"I can speak three languages." (General ability)
✅ Permission (Informal)
"You can use my phone." (Giving permission)
✅ Requests (Informal)
"Can you help me with this?" (Asking for help)
✅ Possibility
"It can get very cold here in winter." (General possibility)
Formation:
Affirmative: Subject + can + verb
• I can play the guitar.
• She can drive a car.
Negative: Subject + cannot/can't + verb
• I cannot (can't) swim.
• He can't speak French.
Question: Can + subject + verb?
• Can you cook?
• Can she come to the party?
📝 3. COULD - Past Ability & Polite Requests
Uses of COULD:
✅ Past Ability (General)
"I could run fast when I was young." (Past general ability)
✅ Polite Requests (More polite than can)
"Could you please open the window?" (Very polite)
✅ Polite Permission
"Could I borrow your pen?" (Polite request for permission)
✅ Possibility (Less certain than can)
"It could rain later." (Possible, not certain)
⚠️ Important: Use 'could' for GENERAL past abilities. For a SPECIFIC achievement in the past, use 'was/were able to' or 'managed to'.
📝 4. BE ABLE TO - Future & Special Situations
Uses of BE ABLE TO:
✅ Future Ability (Can has no future form)
"I will be able to travel next year." (Future ability)
✅ After other modal verbs
"You might be able to solve this problem."
✅ Perfect tenses
"I have been able to finish all my work."
✅ Specific past achievements (instead of could)
"I was able to pass the exam even though it was difficult."
Formation:
Present: am/is/are + able to
• I am able to solve this problem.
Past: was/were + able to
• She was able to escape the fire.
Future: will be + able to
• They will be able to attend the conference.
Present Perfect: have/has been + able to
• We have been able to complete the project.
📊 5. Comparison Table: CAN vs COULD vs BE ABLE TO
Use
CAN
COULD
BE ABLE TO
Present Ability
✅ I can swim.
❌
✅ I am able to swim. (formal)
Past General Ability
❌
✅ I could run fast.
✅ I was able to run fast.
Past Specific Achievement
❌
❌
✅ I was able to pass the exam.
Future Ability
❌
❌
✅ I will be able to come.
Polite Requests
✅ Can you help me?
✅ Could you help me? (more polite)
❌
Permission
✅ You can leave now.
✅ Could I leave early? (polite)
❌
❌ 6. Negative Forms: CAN'T / COULDN'T / WON'T BE ABLE TO
CAN'T (Cannot) - Present Negative
• I can't (cannot) swim. (No ability now)
• She can't come to the meeting. (No permission/possibility)
• You can't park here. (Not allowed)
COULDN'T - Past Negative
• I couldn't (could not) read until I was six.
• She couldn't attend the party because she was sick.
• He couldn't solve the math problem.
WON'T BE ABLE TO - Future Negative
• I won't be able to come tomorrow.
• She won't be able to finish on time.
• They won't be able to attend the wedding.
❓ 7. Question Forms
Yes/No Questions with CAN:
• Can you swim? → Yes, I can. / No, I can't.
• Can she drive? → Yes, she can. / No, she can't.
Yes/No Questions with COULD:
• Could you help me? → Yes, I can. / No, I can't.
• Could she come to the party? → Yes, she can. / No, she can't.
Yes/No Questions with BE ABLE TO:
• Are you able to solve this problem?
• Will she be able to attend the meeting?
WH- Questions:
• What can you do?
• When will you be able to come?
• Why couldn't she attend?
💬 8. 50+ Examples
📌 CAN - Present Ability
1. I can speak three languages: English, Spanish, and French.
2. She can play the piano beautifully.
3. They can run 10 kilometers without stopping.
4. He can solve complex math problems quickly.
5. We can cook Italian food very well.
6. My grandmother can still knit sweaters.
7. Can you fix a broken computer?
8. She can't sing, but she can dance.
9. I can't believe what I just saw!
10. He can remember everything he reads.
📌 COULD - Past Ability
11. When I was young, I could run very fast.
12. She could read before she started school.
13. My grandfather could speak six languages.
14. They could swim across the lake when they were teenagers.
15. I could play chess when I was only five.
16. She couldn't understand the teacher's explanation.
17. He could ride a bicycle at age four.
18. We could see the stars clearly from our old house.
19. Could you hear the music from your room?
20. She couldn't believe her eyes when she saw the surprise.
📌 COULD - Polite Requests
21. Could you please pass me the salt?
22. Could I borrow your pen for a moment?
23. Could you help me with this heavy box?
24. Could she join us for dinner?
25. Could we leave a few minutes early today?
📌 BE ABLE TO - Future & Special Situations
26. I will be able to travel next summer.
27. She won't be able to attend the meeting tomorrow.
28. They were able to escape the burning building.
29. He has been able to save enough money for a new car.
30. Will you be able to finish the project by Friday?
31. Despite the difficulty, she was able to pass the exam.
32. I might be able to come to the party.
33. We haven't been able to contact him since yesterday.
34. She was able to convince her parents to let her go.
35. They will be able to see the results next week.
📌 Permission Examples
36. You can use my laptop if you need it.
37. Can I open the window? It's hot in here.
38. Could I leave work early today?
39. Students can use the library until 9 PM.
40. You can't smoke in this building.
41. Could we have a few more minutes to finish?
42. You can take a break whenever you want.
43. Can I ask you a personal question?
44. You can't enter this area without permission.
45. Could I speak to the manager, please?
❌ 9. Common Mistakes
Mistake
Correction
❌ She can to swim.
✅ She can swim. (No 'to' after modal)
❌ He cans speak English.
✅ He can speak English. (No -s)
❌ I didn't can come yesterday.
✅ I couldn't come yesterday. (No 'didn't' with modals)
❌ I will can do it tomorrow.
✅ I will be able to do it tomorrow. (No future of 'can')
❌ Could you helped me?
✅ Could you help me? (Modal + base form)
💡 Pro Tip: Modal verbs are always followed by the BASE FORM of the verb (no -s, -ed, or -ing) and never use 'to' except for 'be able to'!
✍️ 10. Practice Exercises
Exercise 1: Fill in can, can't, could, or couldn't
1. I ______ swim very well when I was a child.
2. She ______ play the guitar. She's taking lessons.
3. He ______ come to the party because he was sick.
4. ______ you help me with my homework, please?
5. They ______ speak French, but they want to learn.
Exercise 2: Complete with be able to (correct form)
1. I ______ (future) finish the project by tomorrow.
2. She ______ (past) solve the problem after hours of work.
3. They ______ (present perfect) save enough money.
4. ______ you ______ (future) attend the meeting?
5. He ______ (negative future) come to the wedding.
Exercise 3: Choose the correct option
1. (Can / Could) you please close the door?
2. I (can / will be able to) meet you tomorrow.
3. When I was young, I (can / could) run very fast.
4. She (can to / can) speak five languages.
5. They (was able to / could) escape the fire despite the smoke.
❓ Frequently Asked Questions
Q1.What is the difference between 'can' and 'be able to'?▼
'Can' is more common for general abilities in the present. 'Be able to' is used for specific situations or when 'can' is not possible (future tenses, infinitives, perfect tenses). Example: 'I can swim' (general) vs 'I will be able to swim after my lessons' (future).
Q2.When do we use 'could' vs 'was/were able to' for past ability?▼
Use 'could' for general past abilities (I could run fast when I was young). Use 'was/were able to' for specific successful achievements in one situation (I was able to finish the marathon despite the rain).
Q3.Can 'can' and 'could' be used for requests?▼
Yes! 'Can' is more informal and common: 'Can you help me?' 'Could' is more polite and formal: 'Could you please help me?' Both are correct.