1. Lesson Overview
In this lesson, you will study the modal verbs can, could, may, and might, which are commonly used to express ability and possibility.
These modal verbs allow speakers to describe what someone is able to do, what may happen, or what might be possible under certain conditions.
Understanding the subtle differences between these modal verbs helps learners express degrees of certainty, probability, and capability more accurately.
By the end of this lesson, you will be able to:
-
use can and could to express ability
-
use may and might to express possibility
-
distinguish between may and might when describing probability
-
recognise common signal expressions associated with possibility
2. Concept Introduction
Consider the following sentences:
She can solve complex mathematical problems.
The experiment may produce unexpected results.
| Sentence | Meaning |
|---|---|
| She can solve complex problems | expresses ability |
| The experiment may produce results | expresses possibility |
Another example:
The results might change after further analysis.
The modal verb might suggests that the event is possible but uncertain.
3. Core Explanation
Modal verbs such as can, could, may, and might are used to express different meanings depending on the context.
| Modal Verb | Common Meaning |
|---|---|
| can | ability or possibility |
| could | past ability or weaker possibility |
| may | possibility or permission |
| might | lower probability or uncertainty |
Example:
The scientist can analyse complex data.
(ability)
The experiment might fail under extreme conditions.
(possibility)
4. Rule Table
Basic Modal Structure
| Structure | Example |
|---|---|
| subject + modal + base verb | She can analyse the data. |
Negative Structure
| Structure | Example |
|---|---|
| subject + modal + not + base verb | She cannot solve the problem. |
Examples:
The system might not work under extreme pressure.
Interrogative Structure
| Structure | Example |
|---|---|
| modal + subject + base verb | Can she solve the problem? |
Example:
May I ask a question?
5. Usage
1. Ability (Can / Could)
Can describes present ability.
Example:
She can interpret complex data accurately.
Could often describes ability in the past.
Example:
She could solve difficult problems when she was a student.
2. Possibility (Can / Could)
Example:
This method can improve efficiency.
Example:
The results could change after further analysis.
3. Possibility (May / Might)
May suggests moderate probability.
Example:
The experiment may produce new results.
Might suggests weaker probability.
Example:
The experiment might produce new results.
4. Permission (May)
Example:
You may enter the laboratory now.
6. Signal Words
Certain expressions often accompany modal verbs expressing possibility.
| Expression | Example |
|---|---|
| perhaps | The results might change perhaps. |
| maybe | Maybe the system will fail. |
| possibly | The device could possibly malfunction. |
| probably | The results will probably improve. |
| likely | The experiment may likely succeed. |
| unlikely | The system might unlikely fail. |
These expressions indicate degrees of probability.
7. Special Cases
May vs Might
| Modal | Meaning |
|---|---|
| may | higher possibility |
| might | lower possibility |
Example:
The new method may improve the results.
(stronger possibility)
The new method might improve the results.
(less certain)
Can vs Could
| Modal | Meaning |
|---|---|
| can | present ability |
| could | past ability or possibility |
Example:
She can analyse the samples.
She could analyse the samples when she worked in the laboratory.
8. Additional Notes
Modal verbs expressing possibility are often used in scientific discussions, predictions, and academic writing, where certainty may be limited.
Example:
Further research may reveal new information.
This structure allows writers to express careful or cautious conclusions.
9. Common Errors
⚠ Adding “to” after modal verb
Incorrect:
She can to solve the problem.
Correct:
She can solve the problem.
Explanation:
Modal verbs are followed by the base form of the verb.
⚠ Adding third-person “-s”
Incorrect:
She cans solve the problem.
Correct:
She can solve the problem.
Explanation:
Modal verbs do not change form.
⚠ Incorrect verb form
Incorrect:
She can solving the problem.
Correct:
She can solve the problem.
Explanation:
The verb must remain in the base form.
⚠ Incorrect question structure
Incorrect:
Does she can solve the problem?
Correct:
Can she solve the problem?
Explanation:
Modal verbs form questions without auxiliary “do.”
⚠ Confusing may and might
Incorrect:
The results might definitely improve.
Correct:
The results may improve.
Explanation:
Might usually expresses weaker probability.
10. Lesson Mastery
After completing this lesson, you should now be able to:
✅ use can and could to express ability
✅ use may and might to express possibility
✅ distinguish between different degrees of probability
✅ recognise common expressions indicating possibility