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Can & Could

Express ability, possibility, permission, and make polite requests

What are Can and Could?

"Can" and "could" are modal verbs that express ability, possibility, permission, and requests. "Can" is used for present ability, while "could" is used for past ability, polite requests, and hypothetical situations.

Quick Comparison

I can swim (present ability) vs. I could swim when I was 5 (past ability) vs. Could you help me? (polite request).

When to Use CAN vs. COULD

Main Differences

CAN

Present Ability

  • I can speak three languages.
  • She can play the piano.
  • He can run very fast.

General Possibility

  • It can be very cold in winter here.
  • Accidents can happen anywhere.

Permission

  • You can use my phone.
  • Can I leave early today?

Informal Requests

  • Can you help me with this?
  • Can you pass the salt?
vs
COULD

Past Ability

  • I could swim when I was 5.
  • She could speak French before.
  • He could play chess as a child.

Weaker Possibility

  • This could be the answer. (maybe)
  • It could rain later.

Polite Requests

  • Could you help me, please?
  • Could I ask you a question?

Hypothetical Situations

  • If I had time, I could help you.
  • We could go if weather was nice.

Detailed Uses of CAN

Present Ability

Express what you are able to do now.

Ability Examples

  • I can speak three languages.
  • She can play the piano.
  • We can solve this problem.
  • My dog can do tricks.

Detailed Uses of COULD

Suggestions

Use "could" to give gentle suggestions without sounding bossy.

Suggestion Examples

  • You could try calling him again.
  • We could meet at 3 PM instead.
  • She could ask her teacher for help.
  • They could take the train instead.

Formation

Positive Form

Subject + can/could + base verb
  • I can swim. / I could swim when I was young.
  • She can speak Spanish.
  • He could play the guitar.
  • We can help you.

Negative Form

Subject + cannot/could not + base verb
  • I cannot (can't) swim.
  • She could not (couldn't) come yesterday.
  • We can't solve this problem.
  • They couldn't find the address.

Question Form

Can/Could + subject + base verb?
  • Can you swim?
  • Could she speak French?
  • Can they help us?
  • Could you pass the test?

Common Mistakes

Common Mistakes

  • ❌ I can to swim. → ✅ I can swim. (no "to" after modals)
  • ❌ She cans speak English. → ✅ She can speak English. (no -s on modals)
  • ❌ I could helped you. → ✅ I could help you. (base form after modal)
  • ❌ Yesterday I can swim. → ✅ Yesterday I could swim. (use "could" for past)
  • ❌ He doesn't can swim. → ✅ He can't swim. (use "cannot," not "doesn't")

Practice Tips

Practice Tips

  • 🎯 No "to": Never use "to" after can/could. Say "I can swim," NOT "I can to swim."
  • 📝 No -s/-ed: Modals never change form. "He can" (not "cans"), "She could" (not "coulds").
  • 🙏 Politeness: "Could" is more polite than "can" for requests. Use "Could you...?" when asking favors.
  • ⏱️ Time markers: "Can" = now/future. "Could" = past. "I can swim now" vs. "I could swim when I was 5."
  • 💡 Suggestions: Use "You could..." to give gentle suggestions: "You could try studying in the morning."

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