1. Lesson Overview
In this lesson, you will learn how the modal verbs can, could, may, and might express ability and possibility.
These modal verbs help speakers communicate different levels of capability, probability, and uncertainty. They are commonly used in both spoken communication and academic writing.
Example:
She can analyse complex data.
(ability)
The results may change after further testing.
(possibility)
Understanding the differences between these modal verbs allows learners to express precise levels of certainty and capability.
By the end of this lesson, you will be able to:
-
explain how can and could express ability
-
explain how may and might express possibility
-
distinguish between may and might
-
recognise common expressions indicating probability and possibility
2. Concept Introduction
Consider the following examples:
The technician can operate the equipment.
The technician could operate the equipment when necessary.
| Modal | Meaning |
|---|---|
| can | present ability |
| could | past ability / possibility |
Now consider possibility:
The results may change after further analysis.
The results might change after further analysis.
Both express possibility, but might often indicates a weaker probability.
3. Core Explanation
Modal verbs can, could, may, and might express two main meanings:
-
ability
-
possibility
Ability
Ability refers to someone’s capability to perform an action.
Example:
She can solve complex problems.
Past ability is often expressed using could.
Example:
She could solve complex problems when she was a student.
Possibility
Modal verbs can also express uncertainty or probability.
Example:
The experiment may produce different results.
The experiment might produce different results.
Both suggest that the outcome is uncertain.
4. Rule Table
Can and Could for Ability
| Modal | Meaning | Example |
|---|---|---|
| can | present ability | She can analyse the data. |
| could | past ability | She could analyse the data last year. |
May and Might for Possibility
| Modal | Meaning | Example |
|---|---|---|
| may | possible outcome | The results may change. |
| might | weaker possibility | The results might change. |
Comparison of Modal Meanings
| Modal | Function | Example |
|---|---|---|
| can | ability | The researcher can analyse the results. |
| could | past ability / possibility | The researcher could analyse the results earlier. |
| may | possibility | The results may improve. |
| might | weaker possibility | The results might improve. |
5. Usage
1. Present ability
Example:
The technician can operate the new system.
2. Past ability
Example:
The scientist could solve complex problems during the experiment.
3. Possibility
Example:
The results may change after further testing.
4. Weaker possibility
Example:
The results might improve with additional data.
5. Polite permission (with may)
Example:
You may begin the experiment now.
6. Signal Words
Certain expressions often appear in sentences describing possibility or probability.
| Expression | Example |
|---|---|
| perhaps | The results may change. |
| possibly | The system might fail under pressure. |
| maybe | The results may improve later. |
| it is possible that | It is possible that the experiment could succeed. |
| there is a chance that | There is a chance that the results might change. |
These expressions reinforce uncertainty or probability.
7. Special Cases
Could for Present Possibility
Although could often expresses past ability, it can also express present possibility.
Example:
The system could fail if the temperature increases.
May vs Might
Both may and might express possibility, but might often indicates weaker probability.
Example:
The experiment may succeed.
(moderate possibility)
The experiment might succeed.
(less certain)
8. Additional Notes
Modal verbs expressing possibility are frequently used in scientific and academic writing to avoid making absolute claims.
Example:
The results may indicate a correlation between the variables.
This cautious language is common in research reports and academic papers.
9. Common Errors
⚠ Using “to” after a modal verb
Incorrect:
She can to analyse the data.
Correct:
She can analyse the data.
Explanation:
Modal verbs are followed by the base verb without “to.”
⚠ Using incorrect modal for past ability
Incorrect:
She can analyse the data last year.
Correct:
She could analyse the data last year.
Explanation:
Could expresses past ability.
⚠ Confusing possibility with certainty
Incorrect:
The results must change tomorrow.
(if expressing uncertainty)
Correct:
The results may change tomorrow.
Explanation:
Use may/might to express possibility.
⚠ Adding “-s” to modal verbs
Incorrect:
She cans analyse the data.
Correct:
She can analyse the data.
Explanation:
Modal verbs do not change form.
⚠ Using modal without main verb
Incorrect:
The results may.
Correct:
The results may change.
Explanation:
Modal verbs normally require a main verb.
10. Lesson Mastery
After completing this lesson, you should now be able to:
✅ explain how can and could express ability
✅ explain how may and might express possibility
✅ distinguish between may and might
✅ recognise expressions indicating probability and possibility