Understanding how to use can, could, be able to, and be allowed to can be tricky for advanced English learners. Each of these modal verbs and expressions can indicate ability, permission, or possibility, but they are used in specific contexts, and the rules change depending on the situation.
In this article, we will explore the advanced uses of these modal verbs and phrases, with examples to help you master their subtleties.
1. Can: Present Ability and Permission
Can is most commonly used to express ability in the present or permission for something.
Ability:
- She can speak five languages.
- This means she has the ability to speak five languages.
Permission:
- You can leave early today if you finish your work.
- This means you have permission to leave early.
Advanced Use:
Can is also used to make general statements about what is possible:
- It can get really cold in winter here.
- This means that cold weather is possible in winter (a general fact).
2. Could: Past Ability and Polite Requests
Could is the past form of can, but it also serves different functions depending on the context. It expresses past ability or makes polite requests.
Past Ability:
- When I was younger, I could run faster.
- This means you had the ability to run faster in the past.
Polite Requests:
- Could you help me with this task?
- This is a polite way of asking for help.
Advanced Use:
In addition to past ability and requests, could can be used to talk about possibilities in the present or future:
- It could rain tomorrow.
- This means rain is possible, but not certain.
Could is also used in conditional sentences to express hypothetical situations:
- If I had more time, I could travel the world.
3. Be Able To: Ability in All Tenses
While can and could are limited in their tense forms, be able to can be used in all tenses (past, present, and future), making it more versatile for describing ability.
Present Ability:
- I am able to play the piano.
- This is equivalent to saying “I can play the piano” but can be used in more formal contexts.
Past Ability:
- She was able to solve the problem after hours of work.
- This expresses that she succeeded in solving the problem at a specific moment in the past.
Future Ability:
- We will be able to see the results tomorrow.
- This expresses ability in the future.
Advanced Use:
Be able to is often used to describe achievements:
- Despite the obstacles, they were able to complete the project on time.
- This highlights the effort or challenge involved.
In negative sentences, it expresses inability:
- I wasn’t able to finish the report before the deadline.
4. Be Allowed To: Permission in All Tenses
Be allowed to is used to talk about permission. Like be able to, it can be used in various tenses to indicate when permission is given or denied.
Present Permission:
- I am allowed to work from home once a week.
- This means you have permission to work from home in the present.
Past Permission:
- As a child, I wasn’t allowed to stay up late.
- This describes a rule or permission in the past.
Future Permission:
- Will I be allowed to leave early tomorrow?
- This asks if permission will be granted in the future.
Advanced Use:
Be allowed to is often used in more formal contexts, especially in legal or institutional settings:
- Employees are not allowed to use their phones during working hours.
It can also be used to describe permission in hypothetical situations:
- If we finish early, we might be allowed to leave.
5. Comparison: Can vs. Be Able To
One key difference between can and be able to is the range of tenses. While can is mostly used in the present, be able to can express ability across various times.
Examples:
- I can swim. (Present ability)
- I was able to swim when I was 5. (Past ability)
- I will be able to swim soon after I finish my lessons. (Future ability)
6. Comparison: Could vs. Be Allowed To
When talking about past permission, both could and was/were allowed to can be used, but was/were allowed to is more specific when permission was granted for a particular occasion.
Examples:
- When I was a kid, I could stay up late on weekends. (General permission)
- I was allowed to stay up late at my friend’s house. (Specific occasion)
7. Can, Could, Be Able To, Be Allowed To
- Use can to express present ability or permission and could for past ability, polite requests, or hypothetical situations.
- Be able to is more versatile, functioning across all tenses to indicate ability.
- Be allowed to is used for permission in all tenses and is more formal than can or could.
Mastering the nuances of can, could, be able to, and be allowed to will improve your ability to talk about ability and permission in both formal and informal situations.
