1. Lesson Overview
In this lesson, you will learn:
- Form of can and could
- Ability (present and past)
- Permission
- Possibility
- Requests
- Can vs could differences
- Common errors
Modals are followed by the base verb.
2. Form Structure
A. Affirmative
Subject + can/could + base verb
She can solve complex equations.
Scientists could detect the signal.
B. Negative
Subject + cannot (can’t) + base verb
Subject + could not (couldn’t) + base verb
She cannot attend the meeting.
They could not complete the task.
C. Questions
Can/Could + subject + base verb?
Can she solve the problem?
Could they finish the experiment?
3. Uses of Can
A. Present Ability
She can speak three languages.
Scientists can analyze complex data.
B. Informal Permission
You can leave early today.
C. General Possibility
It can be difficult to learn a new language.
4. Uses of Could
A. Past Ability
She could read at the age of four.
B. Polite Requests
Could you help me?
More polite than “can.”
C. Possibility (Less Certain)
It could rain later.
Less certain than “may.”
5. Can vs Could (Comparison)
|
Can |
Could |
|
Present ability |
Past ability |
|
Informal request |
Polite request |
|
Stronger possibility |
Weaker possibility |
Example:
She can solve the problem. (ability now)
She could solve the problem when she was young. (past ability)
6. Important Rule
Modals are followed by the base verb only.
Incorrect:
She can to solve. ❌
She can solves. ❌
Correct:
She can solve.
7. Common Mistakes Spotlight
⚠ Adding “to” after modal
Incorrect: She can to speak English.
Correct: She can speak English.
⚠ Using past form after a modal
Incorrect: She could solved it.
Correct: She could solve it.
⚠ Confusing ability and permission
“May” is more formal for permission.
8. End of Lesson Check
You should now be able to:
- Use can for present ability
- Use could for past ability
- Make polite requests
- Express possibility
- Avoid structural errors